Magnetic Effects of Electric Current Test

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Magnetic Effects of Electric Current Test - 28

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Question 1
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Which of the following figures represents the magnetic lines of force due to an isolated north pole?

A

B

C

D

Solution

By convention, all the magnetic lines of force emerge from north pole and terminate at the south pole.
Hence for a hypothetical case of an isolated north pole, the magnetic lines of force would emerge from it uniformly in all directions.
Question 2
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In a circular current-carrying conductor, if the current flows in the clockwise direction, the magnetic field direction is __________.

A
Parallel to the coil towards the observer

B
Perpendicular to the plane of the coil away from the observer

C
Perpendicular to the plane of the coil towards the observer

D
Parallel to the plane of the coil away from the observer

Solution

The magnetic field are concentric circle at point of a current carrying circular conductor direction of the magnetic field of every section of the circular loop can be found by using the right hand thumb rule .if you curl your right hand fingers in direction of magnetic field your thumb will point in the direction of the current flow.
Question 3
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The magnetic field lines inside a long, current carrying solenoid are nearly:

A
straight

B
circular

C
parabolic

D
elliptical

Solution

As shown in the figure, the magnetic field lines inside a long solenoid are nearly straight lines.
Question 4
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The unit in which we pay the cost of electricity is _____.

A
kilowatt hour

B
watt hour

C
joules

D
ergs

Solution

In our homes electric meter measures electric energy consumed in terms of unit called $$kilowatt\hspace{2mm}hour.$$

$$1kWh=1kW\times 1h$$

$$=1000W\times 3600s$$

$$\implies 1kWh=3.6\times 10^6J$$

Answer-(A)
Question 5
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Consider an experiment where Electric current is flowing in a wire. It is observed that clockwise magnetic field is produced around the wire. A teacher decides to reverse the direction of source battery which results in reversal of electrical current. What will be the effect on magnetic field?

A
Magnetic field disappears

B
Direction of field lines reverse

C
Field lines changes direction to parallel to wire

D
None of the above

Solution

The direction of magnetic field produced by current carrying wire depends on the direction of current in wire.” Magnetic field pattern due to straight current carrying conductor are concentric circles whose center lie on the wire. The direction of magnetic field due to straight current carrying conductor can be determined by Right hand thumb rule.
Using Right Hand thumb rule, as current direction reverses, you need to reverse the hand and direction of magnetic field reverses.
Question 6
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The basic principle of working of motors is

A
Electromagnetic Induction

B
Force on current carrying conductor.

C
Electrostatic Force

D
Heating effect of electric current

Solution

When current is passed through the armature of an electric motor placed in an external magnetic field, it experiences forces along the arms and hence experiences a net torque. The torque causes a constant rotation of the armature.
Question 7
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Consider a current carrying coil placed in a magnetic field. What are the requirements for induced current to flow as per electromagnetic induction.

A
Coil of wire carrying current

B
Change in magnetic field associated with the coil

C
Both A and B

D
None

Solution

When magnetic flux through a coil changes, emf is induced in it. Current carrying coil is not required for above.
Question 8
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Why are multiple fuses used in domestic electric circuit

A
Failure of one of the fuses allow system to continue working in applications where fault has not ocured

B
It increases efficiency of system

C
It guarantees system will always work perfectly

D
All of the above

Solution

A fuse in a circuit prevents damage to the appliances and the circuit due to overloading. Overloading can occur when the live wire and the neutral wire come into direct contact. (This occurs when the insulation of wires is damaged or there is a fault in the appliance.) It is desirable that fault in one part of the system does not affect the entire operation of the power supply. Hence, multiple fuses are used so that failure in some appliances does not affect the performance of other parts of the circuit.
Question 9
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All power entering a house enters via

A
Electricity Meter

B
Various loads in house

C
Electricity board motor

D
Potential Barrier

Solution

In power distribution system at home, all power enters via electricity meter. This is important to charge the correct amount of electricity bill every month.
It correctly measures the amount of electricity used up in house.
Question 10
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What is a commutator?

A
A device that reverses the direction of flow of current through a circuit is called a commutator.

B
A device that flows in the direction of flow of current through a circuit is called a commutator.

C
A device that reverses the direction of flow of voltage through a circuit is called a commutator.

D
All

Solution

A device that reverses the direction of flow of current through a circuit is called a commutator. In electric motors, the split ring acts as a commutator.