# Circular conductor with changing T effecting power and magnetic field

1. Mar 22, 2013

### Helmholtz

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

When we keep a circular copper (ohmic) conductor at a constant temperature T_1, thermal energy is produced along it at a rate P_1 and the magnetic field at its center has magnitude B_1. Then, we heat the conductor to a higher constant temperature T_2 (i.e. T_2>T_1). At temperature T_2, let P_2 and B_2 be the rate of dissipation of energy and the magnitude of the magnetic field at its center respectively. Which of the following is TRUE, if ALL other factors remain the same?

(A) It holds that B_1<B_2 and P_2=P_1.
(B) It holds that B_1>B_2 and P_2<P_1.
(C) It holds that B_1=B_2 and P_2=P_1.
(D) It holds that B_1<B_2 and P_2>P_1.
(E) It holds that B_1=B_2 and P_2>P_1.

2. Relevant equations

Not really sure

3. The attempt at a solution

Looking for a starting point

2. Mar 22, 2013

### Staff: Mentor

You really need to show some effort when posting a question here. At least in your other threads so far, you've shown a bit of effort. Normally this thread would get deleted with a warning, but instead I'll ask a question to try to get you started.

What is the equation for the conductivity of metal versus temperature? That should be enough of a hint to allow you to solve this question.

3. Mar 22, 2013

### Staff: Mentor

BTW, do they specify *how* they are heating the wire? Is it connected to a constant voltage source to produce the current that makes the B field?

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