Q. A loop of wire is placed in a uniform magnetic field. If the magnetic field is increased uniformly, what happens to the induced current in the loop?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
Solution
According to Faraday's law, an increase in magnetic field through the loop induces a current in the loop, which increases as the rate of change of magnetic flux increases.
Q. A loop of wire is placed in a uniform magnetic field. What happens if the magnetic field strength is increased?
A.
Induced current flows in the loop
B.
No effect on the loop
C.
The loop will heat up
D.
The loop will move
Solution
According to Faraday's law of electromagnetic induction, a change in magnetic field strength induces an electromotive force (EMF) in the loop, causing a current to flow.
Correct Answer:
A
— Induced current flows in the loop
Q. A loop of wire is placed in a uniform magnetic field. What happens to the induced EMF if the area of the loop is increased?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Depends on the magnetic field strength
Solution
According to Faraday's law of electromagnetic induction, the induced EMF is directly proportional to the rate of change of magnetic flux, which increases with an increase in the area of the loop.
Q. A loop of wire is rotated in a uniform magnetic field. What is the effect on the induced current? (2019)
A.
It remains constant
B.
It reverses direction
C.
It increases
D.
It decreases
Solution
As the loop rotates, the angle between the magnetic field and the normal to the loop changes, which causes the direction of the induced current to reverse periodically.
Q. A magnetic field is directed into the plane of the paper. If a positive charge moves to the right, what is the direction of the magnetic force acting on it? (2021)
A.
Upwards
B.
Downwards
C.
To the left
D.
To the right
Solution
Using the right-hand rule, if the magnetic field is into the paper and the charge moves to the right, the force will be upwards.
Q. A man can complete a work in 10 days, while another can do it in 15 days. If they work together, how long will it take to complete the work?
A.
6 days
B.
7 days
C.
8 days
D.
9 days
Solution
Work done by the first man in a day = 1/10, second man = 1/15. Together, they do (1/10 + 1/15) = 1/6. Therefore, they will complete the work in 6 days.
Q. A man can complete a work in 10 days. If he works for 3 days and then is joined by another man who can complete the same work in 15 days, how many more days will they take to finish the work?
A.
4
B.
5
C.
6
D.
7
Solution
Work done by the first man in 3 days = 3/10. Remaining work = 1 - 3/10 = 7/10. Combined work rate = 1/10 + 1/15 = 1/6. Time to finish = (7/10) / (1/6) = 4.2 days.
