⚛️ Physics · Topic 3 of 10
Start with the study notes on Electricity & Circuits (definitions, examples and a quick revision), then work through 60 practice questions, each with the correct answer and a clear explanation of why it is right. When you are ready, take this topic as an interactive quiz to test yourself.
Topic overview
An electric cell is a source of electricity. It changes stored chemical energy into electrical energy.
Every cell has two terminals:
Two or more cells joined together make a battery. The positive terminal of one cell touches the negative terminal of the next.
Examples:
Remember: When its chemicals are used up, a cell is “dead”. Ordinary dry cells are replaced; rechargeable cells, like a phone's, can be charged again.
Inside a bulb is a thin coiled wire called the filament. When current flows through it, the filament becomes so hot that it glows and gives light.
A bulb has two terminals, connected to the two ends of the filament.
Cell: chemical energy → electrical energy · Bulb: electrical energy → light (and heat)
Example: If the filament breaks, the bulb is “fused” and will not glow, because the path for the current is broken inside it.
An electric circuit is a complete, closed path along which current flows: from one terminal of the cell, through the wires and the device, and back to the other terminal.
Examples:
A switch opens or closes a circuit. ON closes the circuit; OFF opens it.
Example: The light switch on your wall, or the slide switch on a torch.
Circuits are drawn with standard symbols:
Conductors are materials that let electric current pass through them easily. Most metals are good conductors.
Example: Copper, aluminium, iron and silver.
Insulators are materials that do not let current pass through them.
Example: Plastic, rubber, dry wood, glass and cotton thread.
Make a tester with a cell, a bulb and wires, leaving a gap. Place the material across the gap:
Example: An iron nail across the gap lights the bulb; a plastic spoon does not.
Remember: Electric wires have a copper core to carry the current and a plastic covering to stop it reaching us.
Our bodies conduct electricity, and so does ordinary tap water, because of the salts dissolved in it. This is why electric shocks are dangerous.
An LED (light-emitting diode) is a small light with no filament. Unlike a bulb, it lights only when it is connected the right way round. It uses little energy and stays cool.
Example: Turn the cell round in a bulb circuit and the bulb still glows; turn it round in an LED circuit and the LED goes off.
| Misconception | Correct understanding |
|---|---|
| One wire is enough to light a bulb. | Both terminals of the bulb must be joined to both terminals of the cell. |
| All water is an insulator. | Tap water conducts because of its dissolved salts; only very pure distilled water is a poor conductor. |
| A switch makes or stores electricity. | A switch only opens or closes the path. |
| Turning the cell round stops any bulb. | An ordinary bulb still glows; only an LED depends on direction. |
| Thread or string can replace a wire. | Cotton thread is an insulator, so the circuit stays open. |
Which energy change takes place in a cell?
Chemical energy to electrical energy.
Why does a fused bulb not glow?
Its broken filament leaves a gap, so the circuit is open.
What happens to a circuit when the switch is OFF?
It is open, so no current flows.
How would you test whether a key is a conductor?
Put it across the gap in a tester. If the bulb glows, it conducts.
Why are wires covered in plastic?
Plastic is an insulator, so it stops the current reaching us and prevents shocks.
Why should you never touch a switch with wet hands?
Water conducts electricity, so current could pass through your body.
Why should a torch be switched off when it is not in use?
So that the cells' chemical energy is not used up.
Key takeaway: Current flows only round a closed loop. Conductors carry it; insulators block it and keep us safe.
Notes written by Velnov for Class 6–8 students, following the topics of the NCERT science syllabus.
Q1. easy
A device that stores electricity and provides current in a circuit is a:
Answer: A — Cell (battery)
An electric cell stores chemical energy and converts it into electrical energy, providing current. Two or more cells joined together form a battery.
Q5. easy
The thin wire inside a bulb that glows and gives light is called the:
Answer: A — Filament
The filament is a thin coiled wire (usually tungsten) inside the bulb. When current passes through it, it becomes very hot and glows, producing light.
Q2. medium
An electric cell has two terminals. They are the:
Answer: A — Positive (+) and negative (-) terminals
Every electric cell has a positive terminal (usually a metal cap, +) and a negative terminal (the flat metal disc, -). Current flows out of the positive terminal in a circuit.
Q3. medium
Two or more electric cells joined together form a:
Answer: A — Battery
When two or more cells are connected together (positive terminal of one to negative of the next), they form a battery, which provides more energy than a single cell.
Q7. medium
A bulb has two thick wires called:
Answer: A — Terminals (connected to the filament)
A bulb has two terminals connected to the ends of the filament. These terminals must be connected to the two terminals of the cell for the bulb to light.
Q8. medium
The continuous, closed path along which electric current flows is called an:
Answer: A — Electric circuit
An electric circuit is a complete, closed path (cell, wires, and device like a bulb) through which current can flow continuously.
Q10. medium
In which of these will the bulb NOT glow?
Answer: A — When the circuit is open (broken)
An open (broken) circuit has a gap, so current cannot flow and the bulb stays off. A closed circuit with the switch ON lets the bulb glow.
Q11. medium
A device used to open or close a circuit conveniently (to switch a device ON or OFF) is a:
Answer: A — Switch
A switch is used to make (close) or break (open) a circuit. When the switch is ON, the circuit is closed and current flows; when OFF, the circuit is open.
Q13. medium
Materials that allow electric current to pass through them are called:
Answer: A — Conductors
Conductors (like metals - copper, aluminium, iron) allow electric current to pass through easily. That is why electric wires are made of metal.
Q14. medium
Materials that do NOT allow electric current to pass through them are called:
Answer: A — Insulators
Insulators (like plastic, rubber, wood, glass) do not allow current to pass. They are used to cover wires and make handles of electrical tools safe to touch.
Q17. medium
Why are electric wires covered with plastic or rubber?
Answer: A — To insulate them and protect us from electric shock
The metal inside a wire conducts current, but the plastic/rubber covering is an insulator that prevents current from leaking out, protecting us from electric shocks.
Q18. medium
In a torch, the source of electricity is/are the:
Answer: A — Cells (batteries)
A torch is powered by one or more electric cells (batteries). The cells provide the current that lights the torch bulb when the switch is on.
Q20. medium
If a bulb's filament is broken (fused), the bulb will:
Answer: A — Not glow, because the circuit is broken inside the bulb
A broken filament creates a gap in the circuit inside the bulb, so no current can flow through it. The bulb will not glow - it is 'fused'.
Q22. medium
Our body is a ______ of electricity, which is why electric shocks are dangerous.
Answer: A — Conductor
The human body conducts electricity (mainly because of the water and salts in it). That is why touching live wires can give a dangerous electric shock.
Q24. medium
In a circuit diagram, an electric cell is shown by:
Answer: A — A long line (positive) and a short thick line (negative)
In circuit symbols, a cell is drawn as two parallel lines: a longer thin line for the positive terminal and a shorter thick line for the negative terminal.
Q26. medium
Which energy conversion takes place in an electric cell?
Answer: A — Chemical energy to electrical energy
An electric cell converts stored chemical energy into electrical energy, which then drives the current in a circuit.
Q27. medium
Which energy conversion takes place in a glowing electric bulb?
Answer: A — Electrical energy to light (and heat) energy
In a bulb, electrical energy is converted into light energy (and some heat energy) as current heats the filament until it glows.
Q29. medium
Which of the following is NOT a part of a simple electric torch?
Answer: A — A magnet
A torch contains cells (power), a bulb (light), a switch (to turn it on/off) and a reflector. A magnet is not a part of a simple torch.
Q31. medium
Which of these appliances works using electricity to produce heat?
Answer: A — An electric heater / iron
Electric heaters, irons, kettles and toasters use the heating effect of electric current - current passes through a coil that gets hot and produces heat.
Q33. medium
Which of the following is a safe practice with electricity?
Answer: A — Using insulated (plastic-covered) wires and tools
Using insulated wires and tools with plastic/rubber handles keeps current from reaching us. Touching bare wires, using wet hands, or overloading sockets are all dangerous.
Q35. medium
The device symbol shown as a circle with a cross inside (⊗) usually represents a:
Answer: A — Bulb
In circuit diagrams, a bulb is often drawn as a circle with a cross inside. Learning standard symbols helps in reading and drawing circuit diagrams.
Q37. medium
A 'dry cell' (like an AA battery) is called dry because:
Answer: A — It uses a paste (not a liquid) as its chemical
A dry cell uses a moist paste of chemicals rather than a liquid, making it safe and convenient to use in torches, remotes, clocks and toys.
Q39. medium
What happens to the brightness of a bulb if you use a battery of TWO cells instead of one?
Answer: A — The bulb usually glows brighter
Two cells in series provide more energy (higher voltage) than one, so more current flows and the bulb generally glows brighter (as long as it is within the bulb's safe limit).
Q41. medium
Which of these is an electrical CONDUCTOR found in the human body's surroundings?
Answer: A — Tap water (with dissolved salts)
Ordinary tap water conducts electricity because it contains dissolved salts and minerals. This is why water and electricity together are dangerous. (Note: perfectly pure distilled water is actually a poor conductor.)
Q43. medium
The main function of a switch in a household circuit is to:
Answer: A — Turn appliances on and off by closing or opening the circuit
A switch conveniently makes (closes) or breaks (opens) the circuit, allowing us to turn appliances like lights and fans on or off.
Q45. medium
A bulb connected to a cell does not glow even though the wires are metal and the filament is fine. A likely reason is:
Answer: A — The cell is dead (used up) or a connection is loose
If everything looks fine but the bulb does not glow, the cell may be dead, or a connection (at the terminals or holder) may be loose, breaking the circuit.
Q47. medium
The metal cap at the top of a common AA cell is the:
Answer: A — Positive (+) terminal
The raised metal cap of a dry cell is the positive terminal (+), and the flat metal base is the negative terminal (-).
Q49. medium
Which of the following converts electrical energy mostly into MOTION (mechanical energy)?
Answer: A — An electric fan / motor
An electric fan uses a motor to convert electrical energy into mechanical (motion) energy. A bulb makes light, a heater makes heat, and a cell provides electricity.
Q51. medium
Before the invention of electric bulbs, people mostly used ______ for light.
Answer: A — Oil lamps and candles
Before electricity, homes were lit by oil lamps, candles and lanterns. The electric bulb (invented by Thomas Edison and others) made bright, convenient lighting widely available.
Q53. medium
Which combination is needed to make the simplest circuit that lights a bulb?
Answer: A — A cell, connecting wires, and a bulb (forming a closed loop)
The simplest lighting circuit needs a source (cell), a path (wires), and a device (bulb), all connected in a closed loop so current can flow.
Q55. medium
Electric current is measured with an instrument called a/an:
Answer: A — Ammeter
An ammeter measures the amount of electric current (in amperes) flowing in a circuit. A voltmeter measures voltage; a thermometer measures temperature.
Q57. medium
Which of the following is the correct sequence for current in a simple closed circuit?
Answer: A — Positive terminal of cell → wire → bulb → wire → negative terminal of cell
Conventional current flows from the positive terminal of the cell, through the wires and the bulb, and back to the negative terminal, forming a complete loop.
Q58. medium
Which of these is an electrical INSULATOR used to make safe handles for screwdrivers and pliers?
Answer: A — Plastic or rubber
Handles of electrician's tools are covered with plastic or rubber (insulators) so that current cannot pass to the user's hand, keeping them safe from shock.
Q60. medium
Which of the following statements is TRUE?
Answer: A — A cell provides energy; a bulb uses that energy to give light
The cell is the source of electrical energy; the wires carry the current; and the bulb converts the electrical energy into light. The switch simply opens or closes the path.
Q4. hard
To make a battery, cells are connected so that:
Answer: A — The positive terminal of one cell touches the negative terminal of the next
For cells to work together in a battery, the (+) terminal of one cell is joined to the (-) terminal of the next. This series arrangement adds up their energy.
Q6. hard
The filament of a bulb glows when electric current passes through it because current makes it:
Answer: A — Very hot
The current heats the filament to a very high temperature, making it glow and give off light. This is the heating effect of electric current.
Q9. hard
For a bulb to glow, the electric circuit must be:
Answer: A — Closed (complete, with no gaps)
Current flows only when the circuit is closed (complete). If there is any gap or break (an open circuit), no current flows and the bulb does not glow.
Q12. hard
When a switch is in the 'OFF' position, the circuit is:
Answer: A — Open (broken), so no current flows
In the OFF position, the switch creates a gap in the circuit (open circuit), so current cannot flow and the connected device turns off.
Q15. hard
Which of the following is a GOOD conductor of electricity?
Answer: A — Copper
Copper is a good conductor and is widely used for electric wires. Rubber, plastic and wood are insulators (poor conductors).
Q16. hard
Which of the following is a good INSULATOR?
Answer: A — Rubber
Rubber is an insulator - it does not conduct electricity. Iron, aluminium and silver are all metals and good conductors.
Q19. hard
In a simple circuit, current flows OUT of which terminal of the cell?
Answer: A — The positive (+) terminal
By convention, current in a circuit flows out from the positive (+) terminal of the cell, through the circuit, and back into the negative (-) terminal.
Q21. hard
How can you test whether a material is a conductor or an insulator using a simple circuit?
Answer: A — Place the material in a gap in the circuit; if the bulb glows, it is a conductor
Make a tester circuit with a cell and bulb, leaving a gap. Connect the material across the gap: if the bulb glows, current passed through, so it is a conductor; if not, it is an insulator.
Q23. hard
Why should you NEVER touch electrical appliances or switches with wet hands?
Answer: A — Water conducts electricity, increasing the risk of a shock
Water is a conductor of electricity. Wet hands allow current to pass through the body more easily, greatly increasing the danger of a severe electric shock.
Q25. hard
The chemicals inside an electric cell provide energy. When these chemicals are used up, the cell:
Answer: A — Stops working (goes 'dead') and must be replaced or recharged
A cell converts chemical energy into electrical energy. Once the chemicals are exhausted, it can no longer supply current - it goes 'dead' and is replaced (or recharged, if it is a rechargeable cell).
Q28. hard
In a circuit with a cell and a bulb, if you reverse the connections of the cell, the bulb will:
Answer: A — Still glow (it works in either direction)
A simple bulb glows regardless of the direction of current, so reversing the cell still lights it. (This differs from an LED, which lights only when connected the correct way.)
Q30. hard
Two bulbs are connected one after the other in a single loop with a cell. If ONE bulb fuses, the other bulb will:
Answer: A — Also stop glowing (the circuit is broken)
In a single-loop (series) circuit, all components share one path. If one bulb's filament breaks, the whole circuit is broken, so the other bulb goes off too.
Q32. hard
The coil in an electric heater is made of a special wire that:
Answer: A — Gets very hot when current passes through it (high-resistance wire like nichrome)
Heaters use a high-resistance wire (such as nichrome) that becomes very hot when current flows, converting electrical energy into heat. Nichrome does not melt easily at high temperatures.
Q34. hard
Why do we use metal for the CORE of a wire but plastic for the COVERING?
Answer: A — Metal conducts the current; plastic insulates and protects us
The metal core (usually copper) carries the current because it is a good conductor. The plastic covering is an insulator that prevents shocks and keeps the current inside the wire.
Q36. hard
Which of the following materials will make the bulb glow when placed in a tester circuit?
Answer: A — An iron nail
An iron nail is a metal (conductor), so it completes the circuit and the bulb glows. Rubber, wood and plastic are insulators and would not let the bulb glow.
Q38. hard
If you connect a bulb to a cell using a piece of THREAD instead of wire, the bulb will:
Answer: A — Not glow, because thread is an insulator
Cotton thread is an insulator and does not conduct electricity, so the circuit is not completed and the bulb will not glow. Metal wire is needed.
Q40. hard
Rechargeable cells (like those in mobile phones) differ from ordinary dry cells because they can:
Answer: A — Be charged again and reused many times
Rechargeable cells can be recharged (chemical changes reversed) and used again many times, unlike ordinary dry cells, which are thrown away once used up.
Q42. hard
Which statement correctly describes an OPEN circuit?
Answer: A — It has a break or gap, so no current flows
An open circuit has a gap or break somewhere (e.g., a switch turned off or a loose wire), so the current cannot flow and devices do not work.
Q44. hard
Which of the following correctly lists items ALL of which are conductors?
Answer: A — Copper wire, iron nail, aluminium foil
Copper wire, iron nails and aluminium foil are all metals and good conductors. Plastic, rubber, wood, glass and cotton thread are insulators.
Q46. hard
Why is it dangerous to insert metal objects (like a pin) into an electrical socket?
Answer: A — Metal conducts electricity, giving a dangerous shock
A socket carries a high, dangerous current. Since metal is a conductor, inserting a metal object allows current to flow through it (and you), causing a severe or fatal electric shock.
Q48. hard
An LED (light-emitting diode) differs from a normal bulb because it:
Answer: A — Lights only when connected the correct way (it allows current in one direction)
An LED conducts (and lights up) only when its terminals are connected the right way round. It has no filament, produces little heat, and is very energy-efficient - so it is used in many modern lights.
Q50. hard
Which statement about conductors and insulators is TRUE?
Answer: A — Metals are usually conductors; non-metals like plastic and rubber are usually insulators
Most metals (copper, iron, aluminium, silver) are good conductors, while most non-metals (plastic, rubber, wood, glass) are insulators. This is why wires use metal cores with plastic covers.
Q52. hard
In a circuit, if the two wires from the cell touch each other directly (without a bulb), a large current flows. This is called a:
Answer: A — Short circuit
A short circuit happens when the two terminals are connected by a path of very little resistance (wires touching directly). A large current flows, which can heat the wires dangerously and drain the cell quickly.
Q54. hard
Why should a torch be switched OFF when not in use?
Answer: A — To save the cells (prevent the chemical energy from being used up)
Keeping a torch on drains the cells by using up their chemical energy. Switching it off when not needed makes the cells last longer - an important energy-saving habit.
Q56. hard
Which statement best explains why birds can sit safely on a single electric wire?
Answer: A — They touch only one wire, so no circuit is completed through their body
For current to flow through the bird, it would need to complete a circuit (touch two points at different voltage). Sitting on a single wire, the bird does not complete such a path, so no harmful current flows through it.
Q59. hard
A simple 'electric tester' for checking conductors is made using a cell, some wires and a:
Answer: A — Bulb (which glows if the material conducts)
A tester circuit uses a cell, wires and a bulb with a gap. Placing a material across the gap: if the bulb glows, the material is a conductor; if it stays off, it is an insulator.