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Magnets - 2 (Class X)

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A positively charged particle (alpha particle) projected towards West is deflected towards North by a magnetic field. The direction of magnetic field is

  1. towards North

  2. towards East

  3. downwards

  4. upwards

  5. towards North-East


Correct Option: D
Explanation:

According to Fleming's left-hand rule, the direction of magnetic field is upwards.   

What is the role of commutator rings in an electric motor?

  1. To increase the strength of current flowing

  2. To reverse the direction of current flowing

  3. To increase the strength of magnetic field

  4. To decrease the strength of current flowing

  5. -


Correct Option: B
Explanation:

This is the correct answer. The function of a commutator ring is to reverse the direction of current flowing.

The current produced by moving a straight wire in a magnetic field is called

  1. electric current

  2. induced current

  3. magnetic current

  4. electromagnetic current

  5. -


Correct Option: B
Explanation:

This is the correct answer. Since the current is induced in the wire by moving it in a magnetic field, so it is called induced current.

Which of the following statements about an electromagnet is not true?

  1. It is a temporary magnet.

  2. It produces a much weaker field than a permanent magnet.

  3. Its strength can be easily varied.

  4. Its polarity can be reversed.


Correct Option: B
Explanation:

Electromagnets can produce a very strong magnetic field. Permanent magnets produce a much weaker field than electromagnets.

Which of the following current-detecting devices is used in an electric generator?

  1. Ammeter

  2. Galvanometer

  3. Voltmeter

  4. Nanometer

  5. -


Correct Option: B
Explanation:

This is the correct answer. Galvanometer is used for detecting current in an electric generator.

How can the polarity of an electromagnet be changed?

  1. By changing the number of coils

  2. By changing the intensity of current

  3. By changing the direction of current

  4. By changing the length of the core

  5. -


Correct Option: C
Explanation:

This is the correct answer. Polarity of an electromagnet can be changed by changing the direction of current.

A rectangular coil of copper wire is rotated in a magnetic field. The direction of induced current changes once in every

  1. one revolution

  2. two revolutions

  3. one-fourth revolution

  4. half revolution

  5. -


Correct Option: D
Explanation:

This is the correct answer. When a rectangular copper coil is rotated in a magnetic field, the direction of the induced current changes every half revolution, due to which, the current in the coil remains the same.

Household circuits are connected in ____________ and fuse is connected in __________ with an electrical circuit.

  1. series, parallel

  2. series, series

  3. parallel, parallel

  4. parallel, series

  5. -


Correct Option: D
Explanation:

This is the correct answer. Household circuits are connected in parallel because if there is any problem in the circuit, it will not affect the rest of the circuit. Fuses are connected in series because as soon as the current in the circuit exceeds the maximum value, the fuse wire will melt and prevent fire.

Which of the following appliances works on Fleming's right-hand rule?

  1. Electric mixer

  2. Electric dynamo

  3. Washing machine

  4. Water pump

  5. -


Correct Option: B
Explanation:

This is the correct answer. Electric generator works on Fleming's right-hand rule. Electric dynamo is an electric generator widely used in power stations for producing electric current.

A current-carrying straight conductor is placed along West-East direction. What will be the direction of the force experienced by this conductor due to Earth’s magnetic field?

  1. It will be deflected in the direction of current.

  2. It will be deflected opposite to the direction of current.

  3. It will be deflected vertically downwards.

  4. It will be deflected vertically upwards.


Correct Option: D
Explanation:

The direction of Earth’s magnetic field is from geographical South to geographical North. According to Fleming’s left-hand rule, a current-carrying straight conductor placed along West-East direction will be deflected vertically upwards.

Fleming’s Left hand rulestates that if we  stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor. 

Alternating current produced in India changes its direction in every

  1. 1/100 s

  2. 1/10 s

  3. 1/50 s

  4. 1/20 s

  5. -


Correct Option: A
Explanation:

This is the correct answer. Alternating current changes its direction in every 1/100 s.

Which of the following will not cause overload in a circuit?

  1. Too many appliances connected to one electrical socket

  2. Current flowing equals the capacity of components

  3. Fuse of high capacity connected with low capacity components

  4. When loose and corroded wires are connected in a circuit

  5. -


Correct Option: B
Explanation:

This is the correct answer. This prevents overloading in circuit because current drawn is equal to the maximum capacity of the components.

Which of the following statements is true?

  1. The wire with red insulation is usually the earth wire.

  2. Electric generator works on the principle of electromagnetic induction.

  3. Electric generator converts electrical energy to mechanical energy.

  4. Force experienced by a current-carrying conductor will be maximum when the direction of current is parallel to the direction of the magnetic field.

  5. -


Correct Option: B
Explanation:

This is the correct answer. When a straight conductor is moved in a magnetic field, current is induced in the circuit.

Which of the following appliances, when connected to a circuit, will melt the fuse and break the circuit?

  1. An electric oven of 0.6 kW operated at 220 V having a current rating of 5 A

  2. An electric oven of 2 kW operated at 220 V having a current rating of 6 A

  3. An electric oven of 0.8 kW operated at 200 V having a current rating of 5 A

  4. An electric oven of 1 kW operated at 200 V having a current rating of 6 A

  5. -


Correct Option: B
Explanation:

This is the correct answer. Current drawn by the electric oven, I = P/V = 2000/220 = 9 A. The current exceeds the safe limit of the circuit and hence, the fuse will melt.

What is the force acting on a charge moving along the direction of a magnetic field?

  1. Zero

  2. Negative

  3. Positive

  4. Infinite

  5. Cannot be determined


Correct Option: A
Explanation:

No force acts on a charge moving along the direction of a magnetic field.

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