Sample Test 5. Chapters 8 & 9 - Electricity and Magnetism

1. a. Trace the path most likely taken by the free positive charge, + , in the region of fixed (circled) positive and negative charges in scoring a goal.

b. Show the force arrow on the moving charge at the point of closest approach to each of the fixed charges.

c. What principles did you apply?

2. A toaster (770 watts) and an iron (2200 watts) are operating on the same fused 25 amp, 110 volt circuit. Will the fuse "break" the circuit? Show your reasoning.

3. a. When you walk across a carpet, charges are pulled off the carpet fibers and go onto your body. What kind of excess charge do you have on your body? Why?

b. When your finger then approaches a metal door knob which is uncharged, explain why a spark jumps from your finger to the metal.

4. a. How much energy does 4 coulombs of charge have at a voltage of 8 volts?

b. What is the basic cause of magnetism?

c. Describe two different ways of creating electricity. What is different about the field lines created?

 5. Explain carefully what each of the sections, A, B, and C do to the electricity entering in the plug on the left. Note that both sections B and C use one of the coils.

6. You need to purchase a motor which will be used to raise water from a well which is 20 meters deep. The rope and bucket weighs 50 Newtons and you want to raise water at the rate of 120 kilograms per minute. The motor will be 60 % efficient, What is the wattage of the motor and how much current will it draw from a 110 volt source?

 7. a) In cases A, B, and C, supply the appropriate charge to be placed at each dot that would make the charges move along the path given.
 b) Suppose the + charge on the left is moving with a velocity v toward the + charge on the right which cannot move,. Describe what will happen to the moving charge. Show the direction of the force on it and explain whether the force gets larger or smaller as it moves to the right. Does v increase or decrease?

8. A metal sphere (A) with charge Q is touched to an identical uncharged sphere (B) and then removed. Sphere B is then touched to a third identical uncharged sphere (C). If spheres A and C are then placed a distance r apart, what is the relation you can write (in terms of Q) for the force between them?

9. In each of the cases shown below, indicate what must be true if you observe:

a. Current I flowing in a circular path.

b. Charge q flowing in a circular path.

c. B field formed in a circular path.

10. What is the difference between a motor and a generator:

In terms of energy?

In terms of structure?

11. What must be true for:

Every electric field line?

Every magnetic field line?

Every closed circuit path?

Two appliances plugged into the two outlets of a home wall panel?