# Calculating current

Discussion in 'Homework Help' started by hannah, Jan 30, 2008.

1. ### hannah Thread Starter New Member

Jan 29, 2008
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I dont get this question , can someone show me how to work it out. casue my teacher did not explain it very well in class!!

In a motor vehicle, a relay is used to switch the 12 V , 60 W headlight on and off.

The resistance of the relay coil is 150 ohms . Calculate the current in the relay coil when it is connected to a 12 V supply.

2. ### beenthere Retired Moderator

Apr 20, 2004
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I = E/R - Ohm's law.

3. ### hgmjr Moderator

Jan 28, 2005
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beenthere is correct. Here is a link to the AAC ebook section pertaining to Ohm's Law. Reviewing the material and working through the examples shown should help clear up the topic for you.

hgmjr

4. ### chesart1 Senior Member

Jan 23, 2006
269
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Note that the problem asks for the current through the relay coil. Not through the headlight.

You need to look at the circuit. If a circuit was not provided, then you can assume that the relay coil is not connected to the headlight. The relay contacts connect the headlight to 12 volts. Therefore the information about the headlight is not needed to solve the problem.

5. ### JoeJester AAC Fanatic!

Apr 26, 2005
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1,159
That is all you need to know. Forget the headlight.

6. ### scubasteve_911 Senior Member

Dec 27, 2007
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Is this one of those questions where you are provided more information than you actually need? These always get the people that don't understand the problem and are used to just pluggin in equations

Steve