The magnitude of terminal potential difference?

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Homework Statement



State the magnitude of the terminal potential difference between two supply terminals which are connected to a piece of lead with negligible resistance. The EMF of the circuit is 5000V with internal resistance of 2,000,000 Ohms.

I don't really understand what "magnitude" means and it feels like I'm lacking information.

Homework Equations



I = V/R

V = EMF - Ir

r = 2,000,000 (as it's internal)
EMF = 5000V (given in question)
R = 2,000,000 (no load resistance, just internal)

The Attempt at a Solution



I = V/R = 5000/2000000 = 0.0025 A

Therefore: V = 5000 - (0.0025 X 2000000) = 0

I have no idea if I'm right or not or what this answer is actually telling me.
 

Answers and Replies

  • #2
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What this is telling you is that the emf in the circuit is the pd across the internal resistance and there is no pd "left over" for the terminals or external circuit.
If the lead has negligible (=0) resistance, then by Ohm's Law V=IR, if R is zero then V is zero.
 

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