Question

1.) the magnitude of the magnetic field outside of a solenoid is:

-almost zero

-depends on the type of wire used

-depends on the radius

2.) two wires emerge from a clock face at 90° from the face. One wire is at 3 o’clock and has a current of 2.5 A coming out of the clock face. The other is at 9 o’clock and has a current of 5.0A coming out of the clock face. What can we say about the magnetic field at the center of the clock?

- The B field will be pointed towards 6 o’clock

- The B field will be pointed towards 12 o’clock

- The field will point in a number of different directions

3.) a power transformer with primary coil has 450 loops and the secondary coil has 32 loops what is true about this transformer

-V in> V out

-V in= V out

-v in < V out

Answer 1

Answering 1, and 3.

1. Answer is almost zero.

For an infinite solenoid, you can argue by symmetry that the BB-field outside the solenoid has to be parallel to the axis. From this, by varying the size of the loop used in Ampere's law, you can show that the BB-field outside the solenoid (whatever strength it is) does not vary with distance from the solenoid.

It's pretty easy to show that the BB-field goes to zero from a solenoid, even an infinite one, as the distance from the solenoid goes to infinity. And so the BB-field has to be uniformly zero outside the solenoid.

For a finite solenoid, if you are not close to the ends, you can argue that the missing parts of the infinite solenoid shouldn't affect the BB-field much, and so the field is weak outside the solenoid as compared to inside.

3.