# Homework Help: Electromagnetism and light bulbs

1. Aug 16, 2013

### Zondrina

1. The problem statement, all variables and given/known data

Here's an image of the circuit : http://gyazo.com/b313887dea7780e1226fcc8d4796a63d

1. Explain two ways to make the bulb glow without changing the circuit.
2. Explain why an AC generator replacing the battery could also make the bulb glow.

2. Relevant equations

3. The attempt at a solution

This question is a bit vague, so I wanted to see if I was thinking about this properly.

1. The question says "without changing the circuit". Does that also include the fact I can't close the switch in the first circuit?

If I can close the switch in the first circuit I think I know how to answer this.

If the switch is closed in the first circuit, then increasing current will start flowing through the coils. These coils will induce a magnetic field in the bar magnet which in turn will induce a current in the second coil which will light the bulb.

This increasing current can only continue for so long without blowing the circuit. Eventually the current stops increasing and the magnetic field wont be induced anymore.

So by decreasing the current flowing through the first circuit, we can again induce the magnetic field in the bar magnet which will induce a current in the second coil. This will light the bulb once again until the current decreases to zero. Then we would have to increase the current again to get the magnetic field to come back.

2. An AC generator would produce AC current. AC current is always changing which is the exact condition we need to induce a magnetic field in the bar magnet. This magnetic field will induce a current in the second coil which can be used to light the bulb indefinitely ( until the filament blows ).

Are these okay or am I missing something?

Last edited: Aug 16, 2013
2. Aug 16, 2013

### Staff: Mentor

I think you are allowed to close the switch.

Looks good.

3. Aug 16, 2013

### Zondrina

Thanks :) it really threw me off when they said don't change the circuit.