# Volatage of connected batteries with a switch

Discussion in 'Homework Help' started by drmtrout, Apr 7, 2013.

1. ### drmtrout Thread Starter New Member

Apr 7, 2013
3
0
Two 110-volt storage batteries are connected as shown in the attached picture. The switch has 3 positions: UP, NEUTRAL and DOWN. Based on this information, answer questions 1-3

1. With the switch in its UP position, the voltmeter reading is
A. 110V B. 220V C. zero D. none of the above

2. With the switch in its DOWN position, the voltmeter reading is
A. 110V B. 220V C. zero D. none of the above

3. With the switch in its NEUTRAL position, the voltmeter reading is
A. 110V B. 220V C. zero D. 165V

The answers given is 1-A, 2-B, and 3-C, I think these are the correct answers.

Can't seem to figure out this seemingly simple problem, maybe I'm looking at it from the wrong perspective.

for question #1 with the switch in the up position the way I see it is the volt meter would be connected to the positive to positive and negative to negative ends with no current and 110 volts

for question #2 the circuit would have a current from the + end of one battery to the - end of the other producing a current and a series connection making 220 volts

for question #3 I don't get why the volt meter would read zero as to me it looks identical wether the switch is down or neutral.

Thank you

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2. ### WBahn Moderator

Mar 31, 2012
17,757
4,800
You don't give any indication of which positions are UP, NEUTRAL, and DOWN. So how can we tell what is what? We are not mind readers.

Assuming that the UP is with the top contacts conencted to the center pole in the diagram, the NEUTRAL is the diagram as shown, the DOWN is the bottom set of contacts connected to the center pole, then the answers are correct.

You say that there is no current in the UP case and that there is a current in the DOWN case. Why is there a current in one and not the other?

Redraw the circuit without the switch for each configuration and you will see what is going on.

drmtrout likes this.
3. ### drmtrout Thread Starter New Member

Apr 7, 2013
3
0
I didn't give any indication about the switch because non was given in the problem, I wrote it as it was given. Also ignore the no current statement on my part. I dind't consider the neutral position being as is on the diagram, that does help me understand it better.

So with the switch up it's + to + and - to - and the volt meter providing a parallel circuit, hence 110 volt.

With the switch down it's + to - and hence it's a series, 220 volts.

With the switch in Neutral there is a break in the circuit hence 0 volts.

If that is a correct understanding then my problem was not understanding the proper switch placements, in which case thank you WBahn for clearing that up.

4. ### WBahn Moderator

Mar 31, 2012
17,757
4,800
No problem. It's drawn in a way that is a bit confusing, which I think was intentional.