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CLASS VII SCIENCE
CLASS VII SCIENCE
CHAPTER III: ELECTRICITY: CIRCUITS AND THEIR COMPONENTS
CHAPTER III: ELECTRICITY: CIRCUITS AND THEIR COMPONENTS
Direct Questions Assertion / Reason Correct / Incorrect HOTS Challenging
DIRECT QUESTIONS
DIRECT QUESTIONS
Which component is used to "open" or "close" an electric circuit?
A. Cell
B. Bulb
C. Switch
D. Connecting wire
Answer: C. Switch
In a circuit diagram, a long vertical line and a shorter, thicker vertical line represent:
A. A bulb
B. A switch
C. An electric cell
D. A battery
Answer: C. An electric cell
A combination of two or more cells is called:
A. A circuit
B. A battery
C. A generator
D. A fuse
Answer: B. A battery
The thin wire inside an electric bulb that glows when electricity passes through it is the:
A. Element
B. Filament
C. Lead
D. Connecting wire
Answer: B. Filament
Which of the following is a safety device used to prevent damage to electrical circuits?
A. Switch
B. Fuse
C. Battery
D. Element
Answer: D. Fuse (Note: MCB is also used, but Fuse is the traditional term)
When the switch is in the "OFF" position, the circuit is said to be:
A. Closed
B. Open
C. Complete
D. Short
Answer: B. Open
The heating effect of electric current is used in which of the following?
A. Electric bell
B. Electric iron
C. Electric motor
D. Loudspeaker
Answer: B. Electric iron
Which metal is commonly used to make the filament of an electric bulb?
A. Copper
B. Aluminium
C. Tungsten
D. Iron
Answer: C. Tungsten
An electric current produces a ________ effect when it flows through a wire.
A. Magnetic
B. Chemical
C. Heating
D. All of the above
Answer: D. All of the above
Which device uses the magnetic effect of electric current?
A. Electric heater
B. Electric bell
C. Electric toaster
D. Geyser
Answer: B. Electric bell
A wire becomes ________ when an electric current passes through it.
A. Cold
B. Hot
C. Invisible
D. Liquid
Answer: B. Hot
Which scientist discovered the magnetic effect of electric current?
A. Isaac Newton
B. Hans Christian Oersted
C. Michael Faraday
D. Thomas Edison
Answer: B. Hans Christian Oersted
The full form of MCB is:
A. Miniature Circuit Breaker
B. Main Circuit Board
C. Minimum Current Board
D. Multiple Circuit Breaker
Answer: A. Miniature Circuit Breaker
The coil of wire in an electric heater is known as:
A. Filament
B. Element
C. Fuse
D. Spring
Answer: B. Element
Which of the following does NOT work on the heating effect of current?
A. Electric kettle
B. Immersion heater
C. Electric fan
D. Room heater
Answer: C. Electric fan
An electromagnet behaves like a magnet only when:
A. It is kept in a dark room
B. It is touched by a permanent magnet
C. Electric current flows through its coil
D. It is heated to a high temperature
Answer: C. Electric current flows through its coil
To make a battery of two cells, the negative terminal of one cell is connected to:
A. The negative terminal of the other cell
B. The positive terminal of the other cell
C. The bulb directly
D. The switch only
Answer: B. The positive terminal of the other cell
Which of the following is a good conductor of electricity?
A. Rubber
B. Plastic
C. Copper
D. Wood
Answer: C. Copper
If the filament of a bulb breaks, the bulb is said to be:
A. Charged
B. Fused
C. Switched on
D. Shorted
Answer: B. Fused
The amount of heat produced in a wire depends on its:
A. Material
B. Length
C. Thickness
D. All of the above
Answer: D. All of the above
A current-carrying coil wrapped around a piece of iron is called:
A. A permanent magnet
B. An electromagnet
C. A fuse
D. A battery
Answer: B. An electromagnet
A fuse wire should have a:
A. High melting point
B. Low melting point
C. Very long length
D. High resistance only
Answer: B. Low melting point
What happens to a compass needle kept near a wire when the current is switched on?
A. It gets hot
B. It glows
C. It shows deflection
D. It stops working
Answer: C. It shows deflection
Which mark is used to ensure the safety of electrical appliances in India?
A. AGMARK
B. ISI mark
C. Hallmark
D. ISO
Answer: B. ISI mark
In a battery, the positive terminal is represented by:
A. A thick short line
B. A thin long line
C. A circle
D. A wavy line
Answer: B. A thin long line
Which of the following is an insulator?
A. Iron nail
B. Steel spoon
C. Eraser
D. Gold ring
Answer: C. Eraser
Modern buildings use ________ instead of fuses.
A. CFLs
B. MCBs
C. LEDs
D. Switches
Answer: B. MCBs
The magnetic effect of current was discovered in the year:
A. 1820
B. 1920
C. 1720
D. 1850
Answer: A. 1820
An electric bell works on the principle of:
A. Heating effect of current
B. Chemical effect of current
C. Magnetic effect of current
D. Lighting effect of current
Answer: C. Magnetic effect of current
When the current through a fuse exceeds a certain limit, the fuse wire:
A. Becomes a magnet
B. Melts and breaks the circuit
C. Starts glowing
D. Cools down the circuit
Answer: B. Melts and breaks the circuit
The script "I" in a circuit usually stands for:
A. Insulation
B. Iron
C. Current
D. Intensity
Answer: C. Current
How many terminals does an electric cell have?
A. One
B. Two
C. Three
D. Four
Answer: B. Two
Which of the following is used to save electricity?
A. Filament bulbs
B. LED bulbs
C. Electric heaters
D. High power fuses
Answer: B. LED bulbs
The soft iron core in an electric bell becomes ________ when the circuit is closed.
A. An insulator
B. An electromagnet
C. A permanent magnet
D. A resistor
Answer: B. An electromagnet
Connecting many devices to a single socket can cause:
A. Overloading
B. Under-voltage
C. Magnetism
D. Cooling
Answer: A. Overloading
A fuse is connected in ________ with the circuit.
A. Parallel
B. Series
C. Randomly
D. At the end
Answer: B. Series
Electric current flows from:
A. Negative to Positive terminal
B. Positive to Negative terminal
C. Middle to Ends
D. Any direction
Answer: B. Positive to Negative terminal (Conventional current)
In an electric bell, the ________ hits the gong to produce sound.
A. Coil
B. Hammer
C. Battery
D. Soft iron strip
Answer: B. Hammer
The material used in the heating element of a toaster is usually:
A. Copper
B. Nichrome
C. Tungsten
D. Lead
Answer: B. Nichrome
Which component prevents the cell from being exhausted quickly when not in use?
A. Bulb
B. Wire
C. Switch
D. Fuse
Answer: C. Switch
What is the effect of increasing the number of turns in an electromagnet's coil?
A. Magnetic field decreases
B. Magnetic field increases
C. Magnetic field remains same
D. It becomes a heater
Answer: B. Magnetic field increases
A symbol for a battery of four cells will have how many long lines?
A. One
B. Two
C. Four
D. Eight
Answer: C. Four
Which of the following is a source of electric current?
A. Motor
B. Generator
C. Bulb
D. Bell
Answer: B. Generator
A glowing bulb is ________ to touch.
A. Cold
B. Hot
C. Wet
D. Soft
Answer: B. Hot
If we increase the current in an electromagnet, its strength:
A. Decreases
B. Increases
C. Becomes zero
D. Does not change
Answer: B. Increases
Which device is used to measure electric current?
A. Voltmeter
B. Ammeter
C. Thermometer
D. Speedometer
Answer: B. Ammeter
The path through which electricity flows is called:
A. Way
B. Circuit
C. Road
D. Track
Answer: B. Circuit
A battery of two cells has:
A. 2 positive and 2 negative terminals
B. 1 positive and 1 negative terminal (externally)
C. 4 terminals in total
D. No terminals
Answer: B. 1 positive and 1 negative terminal (externally)
What color is the "live" wire usually coded in modern household wiring?
A. Green
B. Black
C. Red/Brown
D. Yellow
Answer: C. Red/Brown
The flow of electric charges is called:
A. Potential
B. Resistance
C. Electric current
D. Voltage
Answer: C. Electric current
ASSERTION AND REASON
ASSERTION AND REASON
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is not the correct explanation of A.
C. A is true but R is false.
D. A is false but R is true.
Assertion (A): An electromagnet is a temporary magnet.
Reason (R): It loses its magnetism as soon as the current is switched off.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): We should use a piece of copper wire as a fuse.
Reason (R): Copper has a very high melting point.
Answer: D. A is false but R is true.
Assertion (A): The filament of an electric bulb glows when current passes through it.
Reason (R): The filament is made of a material with high resistance that gets white-hot.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): MCBs are preferred over fuses in modern houses.
Reason (R): MCBs automatically switch off when current exceeds the safety limit and can be reset easily.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): A compass needle shows deflection when placed near a current-carrying wire.
Reason (R): Electric current produces a heating effect.
Answer: B. Both A and R are true but R is not the correct explanation of A.
Assertion (A): Connecting too many appliances to a single socket is dangerous.
Reason (R): It can cause overloading and may lead to a fire.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): A battery is a combination of cells.
Reason (R): In a battery, the positive terminal of one cell is connected to the negative terminal of the next.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): Pure water is a good conductor of electricity.
Reason (R): Water contains hydrogen and oxygen.
Answer: D. A is false but R is true (Note: R is true as a fact, but A is false; Distilled water is an insulator).
Assertion (A): Electric bells use electromagnets.
Reason (R): Electromagnets can be turned on and off with a switch.
Answer: A. Both A and R are true and R is the correct explanation of A.
Assertion (A): LED bulbs are more energy-efficient than incandescent bulbs.
Reason (R): LEDs do not work on the heating effect and produce very little heat.
Answer: A. Both A and R are true and R is the correct explanation of A.
CORRECT / INCORRECT STATEMENTS
CORRECT / INCORRECT STATEMENTS
Which of the following statements is INCORRECT?
A. A fuse is a safety device.
B. An electromagnet does not attract pieces of iron.
C. An electric bell has an electromagnet.
D. A battery is a combination of two or more cells.
Answer: B. An electromagnet does not attract pieces of iron.
Identify the CORRECT statement:
A. When the switch is in 'OFF' position, the circuit is closed.
B. Current flows through an open circuit.
C. Symbols are used to represent electric components in a circuit diagram.
D. A fuse wire should have a very high melting point.
Answer: C. Symbols are used to represent electric components in a circuit diagram.
Which of the following about an electromagnet is CORRECT?
A. Its strength cannot be changed.
B. It is a permanent magnet.
C. It can be used to separate magnetic materials from junk.
D. It works on the heating effect of current.
Answer: C. It can be used to separate magnetic materials from junk.
Select the INCORRECT statement regarding electric cells:
A. They have a positive and a negative terminal.
B. They convert chemical energy into electrical energy.
C. They produce a very high amount of electricity compared to the mains.
D. Several cells can be joined to form a battery.
Answer: C. They produce a very high amount of electricity compared to the mains.
Which statement about the heating effect of current is CORRECT?
A. It is used in an electric bell.
B. The heat produced depends on the duration of current flow.
C. Silver is used as an element in heaters.
D. It is an undesirable effect in an electric iron.
Answer: B. The heat produced depends on the duration of current flow.
Identify the INCORRECT statement about fuses:
A. They prevent electrical fires.
B. They must be replaced or reset after they blow.
C. Any ordinary wire can be used as a fuse wire.
D. Fuses have a specific "rating" for the maximum current allowed.
Answer: C. Any ordinary wire can be used as a fuse wire.
Which of the following is a CORRECT statement?
A. Wood is a conductor.
B. Human body is an insulator.
C. Air is generally an insulator.
D. Plastic is a conductor.
Answer: C. Air is generally an insulator.
Select the INCORRECT statement about the electric bell:
A. It uses an electromagnet.
B. It has a contact screw to break the circuit.
C. The gong produces sound when the hammer hits it.
D. It works on the chemical effect of current.
Answer: D. It works on the chemical effect of current.
Identify the CORRECT statement about circuit diagrams:
A. They are artistic drawings of components.
B. They use standard symbols for components.
C. They do not show the direction of current.
D. They are only used for very large machines.
Answer: B. They use standard symbols for components.
Which statement is INCORRECT?
A. CFLs contain mercury vapor.
B. Glowing filaments in bulbs waste energy as heat.
C. A battery of 4 cells has 4 positive terminals connected together.
D. Hans Christian Oersted discovered the magnetic effect of current.
Answer: C. A battery of 4 cells has 4 positive terminals connected together.
HOTS (HIGHER ORDER THINKING SKILLS)
HOTS (HIGHER ORDER THINKING SKILLS)
If you connect a bulb to a battery using a silk thread instead of a copper wire, why will the bulb not glow?
A. Silk thread is too thin.
B. Silk thread is an insulator and does not allow current to flow.
C. Silk thread will catch fire immediately.
D. Silk thread is too expensive.
Answer: B. Silk thread is an insulator and does not allow current to flow.
Why does an electrician wear rubber gloves while repairing an electric switch?
A. To keep his hands clean.
B. To get a better grip on the tools.
C. To prevent getting an electric shock since rubber is an insulator.
D. To keep his hands warm.
Answer: C. To prevent getting an electric shock since rubber is an insulator.
A compass needle shows deflection when placed near a closed circuit. If the direction of the current is reversed, what happens to the needle?
A. It stops moving.
B. It deflects in the opposite direction.
C. It deflects in the same direction.
D. It breaks.
Answer: B. It deflects in the opposite direction.
Why is the fuse wire always placed in the beginning of a household circuit?
A. To save wire.
B. To ensure it breaks the circuit before the current reaches other appliances.
C. To make it easy to see if it's blown.
D. Because it is the cheapest component.
Answer: B. To ensure it breaks the circuit before the current reaches other appliances.
If the number of turns in the coil of an electric bell is doubled, what will be the effect on the sound?
A. No change.
B. The sound may become louder as the electromagnet becomes stronger.
C. The bell will stop working.
D. The bell will produce a lower pitch.
Answer: B. The sound may become louder as the electromagnet becomes stronger.
A fuse blows out repeatedly in a house even after being replaced. This indicates:
A. The fuse wire is of very good quality.
B. There is a short circuit or overloading in the house wiring.
C. The electricity board is sending too little current.
D. The bulb is too bright.
Answer: B. There is a short circuit or overloading in the house wiring.
In a battery of 3 cells, if one cell is put in the wrong direction (positive to positive), what happens?
A. The bulb will glow brighter.
B. The bulb will not glow as the voltages cancel out.
C. The battery will explode.
D. The wires will turn green.
Answer: B. The bulb will not glow as the voltages cancel out.
Why are the elements of electric heaters made of Nichrome instead of Copper?
A. Copper is too expensive.
B. Nichrome has high resistance and a high melting point, allowing it to become red-hot without melting.
C. Copper does not conduct heat.
D. Nichrome is a better magnet.
Answer: B. Nichrome has high resistance and a high melting point, allowing it to become red-hot without melting.
Why do we use symbols in circuit diagrams instead of drawing the actual objects?
A. Because we cannot draw well.
B. Symbols are easier, faster, and understood globally by scientists and engineers.
C. Symbols make the circuit work better.
D. To keep the circuit secret.
Answer: B. Symbols are easier, faster, and understood globally by scientists and engineers.
If you bring a very strong permanent magnet near an electric bell while it is ringing, what might happen?
A. The bell will ring louder.
B. The ringing might get disturbed or stop as the magnetic field is interfered with.
C. The battery will charge faster.
D. The gong will turn into gold.
Answer: B. The ringing might get disturbed or stop as the magnetic field is interfered with.
CHALLENGING QUESTIONS
CHALLENGING QUESTIONS
An electromagnet is used in a crane to lift heavy iron scrap. If the current is suddenly switched off while lifting, what will happen?
A. The crane will move faster.
B. The iron scrap will fall down immediately.
C. The iron scrap will stick to the crane forever.
D. The electromagnet will explode.
Answer: B. The iron scrap will fall down immediately.
In a series circuit with three bulbs, if one bulb's filament breaks, what happens to the other two?
A. They glow brighter.
B. They go out because the circuit is broken.
C. They continue to glow as usual.
D. They flicker.
Answer: B. They go out because the circuit is broken.
What would happen if the contact screw in an electric bell is fixed too tightly and does not lose contact with the iron strip?
A. The bell will ring continuously without stopping.
B. The bell will ring once and then the hammer will stay stuck to the gong.
C. The bell will not ring at all.
D. The battery will explode.
Answer: B. The bell will ring once and then the hammer will stay stuck to the gong.
Which of the following factors does NOT affect the strength of an electromagnet?
A. The number of turns in the coil.
B. The amount of current flowing.
C. The material of the core.
D. The color of the insulation on the wire.
Answer: D. The color of the insulation on the wire.
Why is a fuse wire made of an alloy of tin and lead?
A. To make it shiny.
B. To give it a specific low melting point so it melts when overheated.
C. To make it very strong.
D. To prevent it from rusting.
Answer: B. To give it a specific low melting point so it melts when overheated.
If you have two identical electromagnets, but one is powered by 2 cells and the other by 4 cells, which one will be stronger?
A. The one with 2 cells.
B. The one with 4 cells.
C. Both will be the same.
D. Neither will work.
Answer: B. The one with 4 cells.
What is the purpose of the "Soft Iron Core" inside the coil of an electromagnet?
A. To provide weight.
B. To increase the strength of the magnetic field.
C. To act as an insulator.
D. To prevent the wire from melting.
Answer: B. To increase the strength of the magnetic field.
Why do we say that "Electricity follows the path of least resistance"?
A. Electricity is lazy.
B. Most of the current flows through the path that offers the easiest flow (conductors).
C. Resistance makes electricity move faster.
D. Current only flows through insulators.
Answer: B. Most of the current flows through the path that offers the easiest flow (conductors).
What is the main difference between a cell and a battery?
A. A cell is bigger than a battery.
B. A cell is a single unit, while a battery is a group of cells.
C. A cell is rechargeable, a battery is not.
D. There is no difference.
Answer: B. A cell is a single unit, while a battery is a group of cells.
If a magnetic compass is placed above a wire where current flows from South to North, the North pole of the needle will deflect towards:
A. East
B. West
C. South
D. Downwards
Answer: B. West (According to SNOW rule: South to North Over West)
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