Question

1. The strength of an electromagnet can be increased by

A. Decreasing the number of coils of wire

B.Adding a core of iron to the coil of wire

C.Decreasing the current in the wire

D.All of these

2. Auroras are caused by

A.the van Allen Radiation belts trapping harmful charged particles from space in the Earth’s magnetic field and producing dancing lights.

B.Disturbances in the Earth’s magnetic field, near the poles, which allow charged particles from space to dip into the Earth’s atmosphere, causing a glow similar to fluorescent bulbs.

C.Disturbances in Earth’s magnetic field caused by the “wobble” of the Earth as it spins on its axis which provides the movement in a magnetic field necessary to generate electricity.

3. Two current carrying wires are side by side (parallel), a short distance apart. Will they exert any type of force on each other?

A. Yes, because moving charges produce a magnetic field and the fields of each wire will react.

B.Yes, because charges that are alike repel each other and current involves moving electrons.

C.No, because they would be insulated and electric fields can be shielded.

D.No, because the moving charges are not perpendicular to each other.

4. Which of the following statements is false?

A. Electric charges are always surrounded by a magnetic field.

B. Electric charges are always surrounded by a gravitational field.

C. Electric charges are always surrounded by an electric field.

D. Electric charges can exist alone, but magnetic poles always occur in North/South pairs.

Answer 1

1.  B.Adding a core of iron to the coil of wire

2.  B.Disturbances in the Earth’s magnetic field, near the poles, which allow charged particles from space to dip into the Earth’s atmosphere, causing a glow similar to fluorescent bulbs.

3.  A. Yes, because moving charges produce a magnetic field and the fields of each wire will react.

4.  A. Electric charges are always surrounded by a magnetic field.   

for a charge to exist it has some mass so electric and gravitational lines will always be present but magnetic lines may not always be present