Question

Need help with all 3 questions on Magnetostatics.

1) Two wires are parallel to each other. They will be attracted to each other if:

A) One wire carries a current in the negative direction and the other carries no current

B) One wire carries a current in the positive direction and the other carries no current

C) They carry equal currents but in the opposite direction   

D)They carry currents in the same direction, which do not need to be of the same magnitude

2) Which of the following is NOT true about Ampere’s Law?

A) The differential form involves the electric current density

B)The integral of the magnetic field around the closed contour will be zero if no current passes through the contour.

C) The differential form relates the curl of the magnetic field to the magnetic current density at any point in space

D) The integral form relates to integral of the magnetic field around a closed contour to the electric current passing through the contour

3) Which of the following is true about the magnetic field inside a current-carrying wire?

A) It is maximum at the outer edge of the wire

B) It is maximum at the center of the wire

C) It is constant throughout the wire

D) It is zero inside the wire

Answer 1

1) The two parallel wires attract each other when they carry (equal)currents in oppoistie directions. This is because when they carry current in oppoisite direction the magnetic fluxlines (according to Ampere's Right Hand Thumb rule) will flow in the same direction, adding up, in between the conductors. This will make them attract each other

ANSWER : C

2) The differential form of Ampere's Law relates the curl of Magnetic filed to the Electric Current Density, but not to the Magnetic current density

ANSWER: C

3)The magnetic field is maximum at the ourter edge of the conductor. And from the edge(or surface) of the conductor the magnetic field varies inversly with the distance into the conductor, and with distance out of the conductor

ANSWER: A