# Current in superconductors when a voltage is applied.

1. Feb 26, 2013

### JackA7X

Suppose you a have superconducting loop connected to a 9V battery. What is the current through it? With a resistance of 0Ω, $V = IR$ gives ∞. I don't think that can be right... If it were, $V=\frac{I}{nAe}$ would give an infinite velocity... Does that equation even apply to superconductors?

2. Feb 26, 2013

### marcusl

Current will be limited by the internal resistance of the battery. This happens for all batteries connected to low impedance loads.

3. Feb 26, 2013

### JackA7X

So if we assume the internal resistance is 1.5Ω how do you calculate the current through the superconductor?

4. Feb 26, 2013

### marcusl

I=V/R, just like always. In this case, 9A since a superconductor has 0 resistance.

5. Feb 27, 2013

### syhprum

Marcus
There seems to be an arithmetical error here.

6. Feb 27, 2013

### DrDu

Superconductors can only carry currents lower than a critical current value. If the current rises above that limit, they become normal conducting.

7. Feb 27, 2013

### marcusl

Quite so, I hit the wrong key on my Blackberry. 6A.

8. Feb 27, 2013