Examples

 

Problems

Force on Electric Current in Magnetic Field            Answers

 

Example 1

 

A straight wire 160 meters long is stretched between 2 towers.

 The wire carries 200 A current and the Earth's magnetic field of 5.0x10-5 T makes an angle of 40 degrees with the wire. What is the magnetic force on the wire?

 

Example 2

 

The force on a wire is maximum when it is placed between the pole faces of a magnet. The wire is carrying 9 A, the maximum force is 1.3 N, and the ole faces are 60 cm in diameter. Find the approximate strength of the magnetic field.

 

 

Force on Charge Moving in a Magnetic Field

 

Example 3

 

Given that an alpha particles are emitted from a source at a given speed. You are also given the mass, m, of the alpha particle, its speed, v, and charge, q, and that they are bent into a circular path or radius r.

 

How would you find the magnetic field strength that is required to bend them into a circular path?

 

Magnetic Field of Straight Wire, Force Between Two Wires

 

Example 4

 

Jumper cables - between batteries of 2 cars - are sometimes used to start a stalled vehicle.

Assume that the cable carries a 60 A current and that it can be modelled as a long straight wire. Vacuum permeability, mo = 8.85x10-12C2/N·m2

 

a. How strong is the magnetic field 6.0 cm away from the cable?

b. From above, the Earth's magnetic field is 5.0x10-5 T. How do they compare?

 

Solenoids and Electromagnets

 

Example 5

 

A thin solenoid is 20 cm long and carries a current of 3.0 amps. It has a total of 500 turns of wire.

What is the field inside the solenoid near the center?