# Calculating current in series circuit

1. Dec 27, 2008

### tweety1234

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

can any one please guide me on how to do question 3b? I don't seem to get the right answer. how do i calculate the voltage when the switch is closed if i dont know what the current is?

btw the right answer is 5.77 volts

2. Relevant equations

v=IR?

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2. Dec 27, 2008

### Staff: Mentor

You're given all the information needed to calculate the current.

3. Dec 27, 2008

### tweety1234

okay so would it be like this ;

6/ 10 = 0.6 Amps

but can this value be used for the calculation when the switch is closed?

4. Dec 27, 2008

### Staff: Mentor

No. What's the total resistance in the circuit?

5. Dec 27, 2008

### tweety1234

oh right, but i thought you don't include the internal resistance of the battery if the switch is open ?

6/10.4 = 0.577

0.577 x 0.4 = 0.23 volts

? is this correct?

Last edited: Dec 27, 2008
6. Dec 27, 2008

### tweety1234

oh i got it now , was suppose to multiply by 10 instead of 0.4

thanks for the help

7. Dec 27, 2008

### Staff: Mentor

This problem asks for the voltmeter reading when the switched is closed.

That's the current.

That's the voltage drop due to the internal resistance. But what's the full voltage reading across the battery terminals? (Does that 0.23 volts add or subtract from the battery's emf?)