Magnetic Field & Forces — Practice Quiz

Question 1

A proton (m, q) enters a magnetic field B perpendicular to it with velocity v. Radius of circular path:

Accepted Answer

mv/(qB)

Answer

qB/(mv)

Answer

mv²/(qB)

Answer

qvB/m

Question 2

A charged particle moves in a helical path in uniform B. If pitch is P and radius is R, the speed:

Accepted Answer

(ω/2π)√(P²+4π²R²)

Answer

ωR

Answer

P/T

Answer

2πR/T

Question 3

A wire of length L carrying current I in magnetic field B (perpendicular). Maximum force:

Accepted Answer

BIL

Answer

BIL/2

Answer

BIL²

Answer

B²IL

Question 4

Cyclotron frequency of proton in 1T field (m=1.67×10⁻²⁷ kg, q=1.6×10⁻¹⁹ C):

Accepted Answer

15.3 MHz

Answer

10 MHz

Answer

20 MHz

Answer

30 MHz

Question 5

Two long parallel wires 10 cm apart carry 5A each in same direction. Force per metre:

Accepted Answer

5×10⁻⁵ N/m (attractive)

Answer

5×10⁻⁵ N/m (repulsive)

Answer

10⁻⁵ N/m

Answer

2.5×10⁻⁵ N/m