Hots Questions

## Electromagnetic Induction

- Want to initiate thinking skills? Practice Higher Order Thinking Questions
1
This question explains how a current carrying conductor produces a magnetic field in its surrounding space.
An equilateral triangle of side a is formed from a piece of uniform resistance wire. The current enters in one corner and leaves out of the other as shown in Figure. What is the flux density of magnetic field at the centre O?
A
B
C
Zero
D
2
Concept of electromagnetic induction is the basic principle of working of generators and motors. How emf is induced in the coil of generator or motor and how it produce the required torque to move the rotor. This question explain its working.
A spatially uniform magnetic field of is directed into the plane of the page and perpendicular to it, as shown in the accompanying figure. A wire loop in the plane of the page has constant area m. The magnitude of the magnetic field decreases at a constant rate of T/s. The magnitude and direction of the induced emf is:
A
V clockwise
B
V anticlockwise
C
V anticlockwise
D
V clockwise
A rectangular coil of turns is perpendicular to a uniform magnetic field. If the field is reversed in a short time interval of t, then find the value of given the charge flowing through the wire is independent of time.
A
1
B
- 1
C
zero
D
2
3
There are three ways to change the magnetic flux through a loop:
Change the magnetic field strength (increase, decrease) over the surface area.
Change the area of the loop (increase by expanding the loop, decrease by shrinking the loop).
Change the angle between the surface defined by the loop and the magnetic field vector. Remember that flux is the integral of the dot product between B and dA.
Solve problems where circuit is rotating in the plane of magnetic field.
A coil of 1200 turns and mean area of 500 is held perpendicular to a uniform magnetic field of induction T. The resistance of the coil is 20 ohms. When the coil is rotated through  in the magnetic field in 0.1 s, the average electric current (in mA) induced is :
A
12
B
24
C
36
D
48
A magnetic flux of   passing through a turns coil is reversed in  seconds. The average emf per unit area induced in the coil in is
A
B
C
D
In a coil of area and turns with magnetic field directed perpendicular to the plane and is changing at the rate of gauss/ second. The resistance of the coil is . The current in the coil will be
A
B
C
D

4
Self inductance is the characteristic of the coil itself. Mutual inductance is the characteristic of a pair of coils. The induced current opposes the decay of current in the coil when the main current in the coil decreases. Charging of capacitor and inductive circuit work on the principle.
The e.m.f. induced in a secondary coil is when the current breaks in the primary coil. The mutual inductance is and the current reaches to zero in sec in the primary.The maximum current in the primary before it breaks is
A
B
C
D
A solenoid (air core) ahs 400 turns, is 20 cm long and has a cross section of . Then the coefficient of self induction is approximately
A
B
C
D
5
Series having capacitor and an ideal inductor has applications in radio and communication engineering. They can be used to select a certain narrow range of frequencies from the total spectrum of ambient radio waves. It consists of an inductor (L), capacitor (C) and resistor (R) connected in series or parallel. Let's see a problem to understand how it works.
In the circuit shown the capacitor and an ideal inductor do not have energy initially and key is switch on at . Then which of the following options is/are true:
This question has multiple correct options
A
Potential difference across the capacitor at is zero
B
The current flowing through the battery at is
C
Potential difference across the inductor at is zero
D
The current flowing through the battery at is A
6
DC motors are common in small household appliances such as vacuum cleaners, cordless power tools, and food mixers. We will see how it works.
A flat coil ABCD is freely suspended between the pole pieces of a U-shaped permanent magnet with the plane of coil parallel to the magnetic field. Name an instrument which makes use of the principle stated above.
A
a.c. motor
B
d.c. motor
C
m.c. motor
D
None of the above
7
AC generators power home electrical appliances and small motors such as water pump etc. in households. Describe the principal, construction and working of a single-phase AC generator.
Describe the principal, construction and working of a single-phase AC generator