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50 questions · 1 auto-graded MCQ + 49 self-marked written.

Question 11 Mark
Will the compass needle show deflection when the switch in the circuit shown by figure is closed?

Image

Answer
No.

The given circuit does not have any current source. In the absence of current, the wire does not behave as a magnet and hence, the compass needle will not show any deflection.

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Question 21 Mark
Name any two effects of electric current.
Answer
The two effects of electric current are
$1)$ Heating effect of electric current
$2)$ Magnetic effect of electric current
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Question 31 Mark
In the circuit shown in figure
Image
What will be the order in which the bulbs $A, B$ and $C$ will glow when the switch is moved to the $‘ON’$ position?
Answer
Bulbs will glow simultaneously.When the switch is moved to the $‘ON’$ position, then all the bulbs will glow at once.
This is because they all are connected to the same battery and switch.
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Question 41 Mark
In the circuit shown in figure
Image
Would any of the bulbs glow when the switch is in the $‘OFF’$ position?
Answer
No.When the switch is in $‘OFF’$ position, the current does not flow through the circuit. Hence, none of the bulbs will glow.
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Question 51 Mark
Name the scientist who discovered the magnetic effect of electric current.
Answer
The scientist who discovered the magnetic effect of electric current is Hans Christian Oersted.
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Question 61 Mark
Mark $‘T’$ if the statement is true and $‘F’$ if it is false: An electric bell has an electromagnet. $(T/F)$
Answer
True.
An electric bell has a piece of iron wound by a coil. When current passes through this coil, it behaves as an electromagnet.
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Question 71 Mark
Fill in the blanks:When current is switched ‘on’ in a room heater, it _______.
Answer
When current is switched ‘on’ in a room heater, it produces heat.
Working of a room heater is based on the phenomenon of heating effect of electric current.
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Question 81 Mark
Why are fuse wire not used in circuit containing electric cell?
Answer
Fuse wire is used to prevent sudden excess flow of current. Cell provide current of fix magnitude So fuse wire are not used in circuit containing electric cell.
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Question 91 Mark
Enlist some appliances that work on the property of the magnetic effect of electric current.
Answer
Electric Bell, Motor, Fan etc.
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Question 101 Mark
What is an electric fuse?
Answer
An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it.
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Question 111 Mark
What is magnetic field?
Answer
The region around the magnet, where force of attraction or repulsion can be felt by magnetic materials, is called as magnetic field.
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Question 121 Mark
Electromagnets are better than permanent magnets. Explain why.
Answer
An electromagnet can be switched $OFF$ or switched $ON$ as desired and this is not possible in the permanent magnets. That is why the electromagnets are better than the permanent magnets.
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Question 131 Mark
Name some electric appliances where the heating effect of the electric current is used.
Answer
Some of the electric appliances where the heating effect of the electric current is used are electric heater, geyser, micro-oven, room heater, boiler, etc.
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Question 141 Mark
A current through a horizontal power line flows in north to south direction. What is the direction of magnetic field?
  1. At a point directly below it.
  2. At a point directly above it.
Answer
  1. West to East.
  2. East to West.
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Question 151 Mark
Two magnetic lines of force don’t intersect each other. Explain why?
Answer
If two magnetic lines of force will intersect each other then, at the point of intersection there will be two different directions of magnetic field which is not possible.
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Question 161 Mark
By inserting the steel bar inside the solenoid and switching on electric current.
Answer
Magnitude of electric current, perpendicular distance between that point and conductor.
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Question 181 Mark
Name a safety device in domestic circuit used to prevent electrical fire due to short circuit or overloading.
Answer
Electric fuse.
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Question 191 Mark
How fuses are useful?
Answer
A fuse is thus a safety device which prevents damages to electrical circuits and possible fires.
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Question 201 Mark
Fill in the blanks:The safety device based on the heating effect of electric current is called a _____.
Answer
The safety device based on the heating effect of electric current is called a fuse.
Fuse is a safety device, which limits current in circuit and breaks the circuit if the current exceeds its maximum limit.
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Question 211 Mark
For a bulb to glow, it must be connected to a battery. Why?
Answer
For a bulb to glow, it must be connected to a battery because a bulb will require more power. The battery is the source of electric current in a circuit which glows the bulb. Hence, the battery is essential in a circuit.
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Question 221 Mark
Differentiate between electric current and electric circuit.
Answer
Electric Current is the flow of electrons. But an electric Circuit is the closed path in which electric current flows.
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Question 231 Mark
Mark $‘T’$ if the statement is true and $‘F’$ if it is false:
When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. $(T/F)$
Answer
True.
The wire of the fuse is made of special material which has a low melting point.
When large current passes through a fuse, it melts quickly and breaks the circuit.
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Question 241 Mark
Name the device used these days in place of eiectric fuses in electrical circuits.
Answer
The device used in these days in place of electric fuse is $MCB$ (Miniature Circuit Breaker).
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Question 251 Mark
Fill in the blanks: An electric cell produces electricity from the _____ in it.
Answer
An electric cell produces electricity from the Chemicals stored in it.
Chemicals stored, an electric cell is a device capable of changing chemical energy into electrical energy (electricity).
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Question 261 Mark
Would any of the bulbs glow when the switch is in the 'off' position in a circuit?
Answer
None of the bulb will glow when the switch is in the 'off' position as there will be no electric current in the circuit.
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Question 271 Mark
On what factors does the heat produced in a wire depend?
Answer
The heat produced in a wire depends on the current flowing in the wire and the resistance of the wire.
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Question 301 Mark
Why is a good fuse wire made of tin?
Answer
A good fuse wire is made of tin as it has a low melting point.
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MCQ 311 Mark
When an electric current flows through a copper wire $AB$ as shown in Figure, the wire.
  • A
    Deflects a magnetic needle placed near it.
  • B
    Becomes red hot.
  • Gives electric shock.
  • D
    Behaves like a fuse.
Answer
Correct option: C.
Gives electric shock.
Gives electric shock.
It deflects a magnetic needle placed near it because a magnetic field is created when the current passes through it.
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Question 321 Mark
State some factors that affect production of heat in a wire through which an electric current is passing.
Answer
Length and thickness of the wire, the duration of flow of current, and the material of the wire.
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Question 331 Mark
State whether the bulb glows when the circuit is opened.
Answer
No, the bulb does not glow when the circuit is opened. The bulb glows only when the circuit is closed.
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Question 341 Mark
How we can show that magnetic field exist around a wire carrying current?
Answer
By using magnetic compass which, shows deflection.
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Question 351 Mark
Why is an electric fuse required in all electrical appliances?
Answer
Electric fuse is required in all electrical appliances to prevent damage from excessive current flow and during short circuit.
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Question 361 Mark
A fuse is connected with a live wire or with neutral wire?
Answer
Fuse is always connected with live wire.
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Question 371 Mark
What is the fuse rating in the lighting and fans circuit of a small house?
Answer
The fuse rating is the maximum current that the fuse can carry without melting.
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Question 381 Mark
What is a battery?
Answer
A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another.
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Question 401 Mark
Mark $‘T’$ if the statement is true and $‘F’$ if it is false: An electromagnet does not attract a piece of iron. $(T/F)$
Answer
False.
working of an electromagnet is based on the magnetic effect of electric current.
An electromagnet behaves as a magnet when current passes through it. Hence, it will attract a piece of iron.
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Question 411 Mark
What do you mean by electromagnetic induction?
Answer
The process, due to which a changing magnetic field in a conductor induces a current in another conductor, is called electromagnetic induction.
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Question 421 Mark
What is an electromagnet?
Answer
An electromagnet is a coil of wire wound on a soft iron core which acts as a magnet due to the magnetic field of electric current.
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Question 431 Mark
If cells are placed side by side. Then, how are the terminals of the cells connected?
Answer
If cells are placed side by side, then with the help of some connecting wires, the positive terminal of one cell is connected to the negative terminal of other to produce a combined power of all cells which can be called a battery.
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Question 441 Mark
Mention the name of the two devices that work on the basis of magnetic effects of current.
Answer
The devices that work on the basis of magnetic effects of current are loudspeaker and electric bell.
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Question 451 Mark
What is a circuit diagram?
Answer
In an electrical Circuit when we replace electrical components with their symbols we call it Circuit diagram.
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Question 461 Mark
The nails attract the pins. Comment.
Answer
When the current is passed through the wire wound on the nail, it behave as electromagnet. Due to this reason, the nails attract the pins.
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Question 471 Mark
Can we use an electromagnet separating plastic bags from a garbage heap? Explain.
Answer
An electromagnet cannot be used for separating plastic bags from a garbage heap as it attracts only iron pieces and will not attract plastic bags.
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Question 481 Mark
Which of the two absorbs more radiation a dark coloured object or a light coloured object?
Answer
Heating effect of electric current and magnetic effect of electric current.
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Question 491 Mark
Give the name any two electrical appliances in which electromagnets are used.
Answer
Electric fan and electrical motor are the electrical appliances in which electromagnets are used.
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Question 501 Mark
How can a solenoid be used to magnetize a steel bar?
Answer
By inserting the steel bar inside the solenoid and switching on electric current.
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1 Marks Question - Science STD 7 Questions - Vidyadip