Question

A circular loop of conducting wire contains a small bulb in a complete circuit (with no battery or any voltage source). This loop with bulb is lying on a table next to (but not touching) a long straight wire. The following process take place in the long straight wire: There is a constant current of 8.0 Amps for 30 seconds, then the current decreases to 2.0 Amps in 0.040 seconds, and finally stays at 2.0 A for one minute. Choose the correct response that describes the most likely observations of the small bulb. 

• The bulb is dark the whole time except for a small flash of light during the time the current drops from 8.0 to 20 A. 

• The bulb starts off very bright for the first 30 seconds, dims quickly, then stays dim for the final minute. 

• The bulb starts off very bright for the first 30 seconds, flashes brightly, then goes dim for the final minute. 

• The bulb never shows any light during any phase of this process. 

• The bulb starts off very bright.goes off for the 0.040 sec when the current in the wire changes, then comes back on dimmer for the final 2 minutes.

 

Question 18 

Three wires (X, Y, Z) each of length 1.6 m are lined up (like fence posts) in a row with wire Y midway between wires X and Z. Wire X has a current of 3.0 A toward the ground, wire Y has a current of 1.0 A toward the ground, and wire Z has 9.0 A toward the ceiling. If wires X and Z are 80.0 cm apart, what is the net magnetic field strength due to the three wires at a point midway between wires X and Y? 

• 7.0E-6 T 

• 5.0E-6 T 

• 1.0E-6T 

• 7.5E-7T 

• 2.5E-6

Answer 1

Answer 2