TUTORIAL 8: MAGNETISM
1. A straight power line carries 30 A and is perpendicular to the Earth’s magnetic field
of 0.5 x 10-4 T. What magnitude force is exerted on 100 m of this power line?
2. A 12 cm segment of wire carries a current of 4.0 A directed at an angle of 41° north
of westerly B field. What must be the magnitude of the B field if it is to produce a 5 N
force on this segment of wire? What is the direction of force?
3. A proton moving at 4.00 × 106 m/s through a magnetic field of 1.70 T experiences a
magnetic force of magnitude 8.2 × 10-13 N. What is the angle between the proton’s
velocity and the field?
4. An electron moves with a velocity of 5 × 105 m/s at an angle of 60° with an eastward
B field. The electron experiences a force of 3.2 × 10-18 N directed into the paper.
What is the magnitude of B?
5. Suppose that the magnetic field of the earth were due to a single current moving in a
circle of radius 2000 km through the Earth’s molten core. The strength of the earth’s
magnetic field on the surface near a magnetic pole is about 6 × 105 T. About how
large a current would be required to produce such field?
6. Two parallel straight wires 10.0 cm apart carry current I1 = 5.0 A and I2 = 7.0 A with
direction into the page. Determine the magnitude and direction of the magnetic field
halfway between the two wires.
7. Find the direction and magnitude of the net magnetic field at point B due to the two
wires shown in figure. Wire 1 carries 𝐼1 = 650 mA and wire 2 carries 𝐼2 = 475 mA.
Answer:
(1) 0.15 N
(2) 15.9 T, out of page
(3) 48.9 or 131.1
(4) 46  T
8
5) Ans : 6 10 A
6) Ans : 0.8 10
−5
T
7) 1.16 × 10-7 T, 158.2