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Electromagnetism

Description: electromagnetism
Number of Questions: 18
Created by:
Tags: electromagnetism Electromagnetism Magnetic Field around a Straight Conductor carrying Current Magnetic Field around a Solenoid
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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 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.

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 nature of magnetic field near a long current-carrying straight wire?

  1. These are straight lines perpendicular to the wire.

  2. These are straight lines parallel to the wire.

  3. These are radial lines originating from the wire.

  4. These are concentric circles centred around the wire.

  5. -


Correct Option: D
Explanation:

This is the correct answer. Magnetic field around a current-carrying straight wire is concentric in nature whose centre is the wire.

Magnetic field inside a long straight solenoid carrying current

  1. is same at all the points

  2. is zero

  3. increases as we move towards its ends

  4. decreases as we move towards the centre

  5. -


Correct Option: A
Explanation:

This is the correct answer. Magnetic field produced in a long straight solenoid carrying current is uniform at all the points.

Where is the strength of a magnetic field greatest in a circular current-carrying conductor?

  1. Tangent to the wire

  2. Parallel to the wire

  3. Perpendicular to the wire

  4. Centre of the wire

  5. -


Correct Option: D
Explanation:

This is the correct answer. The strength of the magnetic field is the greatest at the centre as all lines of force add up to each other.

Which medical examination is based on magnetism produced in the body?

  1. MRI scan

  2. Ultra sound

  3. MCR scan

  4. CT scan

  5. -


Correct Option: A
Explanation:

This is the correct answer. An MRI (or magnetic resonance imaging) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures.

Magnetic field produced in a bar magnet is similar to

  1. a straight current-carrying conductor

  2. a solenoid

  3. an electromagnet

  4. a circular coil carrying current

  5. -


Correct Option: B
Explanation:

This is the correct answer. The magnetic field produced in a bar magnet is similar to a solenoid.

A charge particle projected towards east is deflected towards north by a magnetic field. What is the direction of the magnetic field?

  1. Towards east

  2. Towards west

  3. Downwards

  4. Upwards

  5. -


Correct Option: C
Explanation:

This is the correct answer. According to Fleming's left hand rule: Hold out your left hand with forefinger, middle finger and thumb at right angle to one another. If the fore finger represents the direction of the field and the middle finger represents the direction of the current, then thumb gives the direction of the force. In this case, the direction of the charge particle is towards east, i.e. the direction of the current repesented by the fore finger and the thumb repesents the direction of the force. The fore finger represents the direction of the magnetic field.

A copper coil is placed between N and S poles of a magnet and connected to a galvanometer. In which of the following conditions will there be no deflection in the galvanometer?

  1. N pole of the magnet is moved inwards.

  2. Coil and magnet both are stationary.

  3. Coil is moved upwards.

  4. S pole of the magnet is moved outwards.

  5. -


Correct Option: B
Explanation:

This is the correct answer. When there is no movement in either the magnet or the coil, there will be no induced current in the circuit and hence no deflection.

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