Physics 222 Worksheet: Chapter 20, Magnetism

1) Which of the following does not produce a magnetic field?

a) ferrous materials

b) charges at rest

c) moving charges

d) electric current

2) Which of the following statements best describes magnetic and electric fields?

a) electric fields begin and end on charges and magnetic fields form closed loops.

b) magnetic fields begin and end on charges and electric fields form closed loops.

c) electric fields begin and end on charges at rest and magnetic fields begin and end on moving charges.

3) The magnetic force on a moving charge is able to

a) change both the speed and direction of the charge.

b) change the speed but not the direction of the charge.

c) change the direction but not the speed of the charge.

4) The magnetic field at a distance of 1.0 cm from a wire is 0.6 T. At a distance of 2.0 cm it is

a) 1.2 T

b) 2.4 T

c) 0.3 T

d) 0.15 T

5) The magnetic field near a current

a) is directed radially away from the wire

b) forms a loop around the wire

c) is directed parallel to the wire

6) A wire is carrying current to the north. The magnetic field directly  below the wire is directed

a) up

b) down

c) to the east

d) to the west

e) to the north

f) to the south

7) A positive charge moving to the east enters a magnetic field directed straight up. The magnetic force on the charge is directed

a) up

b) down

c) to the east

d) to the west

e) to the north

f) to the south

8) Which of the following depends upon magnetism in order to operate?

a) capacitor

b) battery

c) semiconductor

d) electric motor

Ans: 1-b, 2-a, 3-c, 4-c, 5-b, 6-d, 7-f, 8-d

Physics 222 Worksheet: Magnetic Forces

Calculate the magnitude and direction of the force on the wire. In each case I = 2.00 A, B = 0.100 T, l = 0.300 m. The z - axis is directed out of the page.

y

y

	x

Ans: 0.0600 T, +z dir Ans: 0.0600 T, +x dir

x

Ans: 0.0520 T, -z dir Ans: 0.0600 T, -y dir

	x

Ans: 0.0600 T, in the xz plane 30⁰ from +z axis Ans: 0.0600 T, in the xy plane 30⁰ from +y axis