Magnets and Magnetic Fields - Jamb Physics Past Questions and Answers

Question 36:

• JAMB 2001

The force on a current carrying conductor in a magnetic field is greatest when the

A. Conductor makes an angle of 60° with the field
B. Force is idependent of the angles between the fields and the conductor
C. Conductor is parallel with the field
D. Conductor is at right angle with the field

Question 37:

• JAMB 2003

A magnetic field is said to exist at a point if a force is

A. Exerted on a stationary charge at the point
B. Exerted on a moving charge at the point
C. Deflected at the point
D. Strengthened at the point

Question 38:

• JAMB 2003

I It retains its magnetic much longer than steel.
II It is more easily magnetized than steel
III It is more easily demagnetized than steel
IV It produces a stronger magnet than steel
Which combination of the above makes iron preferable to steel in the making of electromagnets?

A. I and II only
B. II and III only
C. I, III, and IV only
D. II, III and IV only

Question 39:

• JAMB 2003

A circuit has an area of 0.4m² and consists of 50 loops of wire. If the loops are twisted and allowed to rotate at a constant angular velocity of 10 rad s^-1 in a uniform magnetic field of 0.4T, the amplitude of the induced voltage is

A. 8V
B. 16V
C. 20V
D. 80V

Question 40:

• JAMB 2003

The force on a charge moving with velocity v in a magnetic field B is half of the maximum force when the angle between v and B is

A. 90^o
B. 45^o
C. 30^o
D. 0^o