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saw176
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Homework Statement
Two 9.4 k-ohm resistors are placed in series and connected to a battery. A voltmeter of sensitivity 1000 ohm/V is on the 3-V scale and reads 2 V when placed across either resistor. What is the emf of the battery? (Ignore it's internal resistance)
Homework Equations
V=IR
Emf = IR
The Attempt at a Solution
First of all, I'm kind of unsure what "on the 3-V scale" means. My guess is that it means it takes 3 volts for a full-scale deflection of the voltmeter? Because it has a sensitivity of 1000 ohm/V and is reading 2 volts:
I = V/R
I = 2 V / 2000 ohm
I = 1 x 10-3A
Then I tried to find the total resistance of the circuit, first with the voltmeter and one resistor in parrallel and the other resistor in series:
1/R = 1/9.4 k-ohm + 1/2000 ohm = 1.65 k-ohm
R = 1.65 k-ohm + 9.4 k-ohm = 11.1 k-ohm
Finally, I went Emf = IR
Emf= 1 x 10-3 (11.1 k-ohm)
Emf = 11.1 V
The correct answer is 10 V, so my answer is close, but I am unsure if that's just by chance, because I never actually used the fact that the voltmeter is "on the 3.0 V scale". I really have no idea if my thought process is correct for this problem, am I on the right track?
Thanks!