Question 1

If the magnetic field   is uniform over the area bounded by a circle with a radius R, the net current through the circle is:

Accepted Answer

A)  0 
B)  2 $\pi$RB$\mu$0 
C)   $\pi$R2B/$\mu$0 
D)  RB/2$\mu$0 
E)  2RB/$\mu$0 
A)  0 
B)  2 $\pi$RB$\mu$0 
C)   $\pi$R2B/$\mu$0 
D)  RB/2$\mu$0 
E)  2RB/$\mu$0

Question 2

Which graph correctly gives the magnitude of the magnetic field outside an infinitely long straight current-carrying wire as a function of the distance r from the wire?

Accepted Answer

A)  I 
B)  II 
C)  III 
D)  IV 
E)  V 
A)  I 
B)  II 
C)  III 
D)  IV 
E)  V

Question 3

A solenoid is 3.0 cm long and has a radius of 0.50 cm. It is wrapped with 500 turns of wire carrying a current of 2.0 A. The magnetic field at the center of the solenoid is:

Accepted Answer

A)  9.9 * 10-8 
B)  1.3*10-3 
C)  4.2*10-2 
D)  16 T 
E)  20 T 
A)  9.9 * 10-8 
B)  1.3*10-3 
C)  4.2*10-2 
D)  16 T 
E)  20 T

Question 4

The magnetic field B inside a long ideal solenoid is independent of:

Accepted Answer

A)  the current 
B)  the core material 
C)  the spacing of the windings 
D)  the cross-sectional area 
E)  the direction of the current 
A)  the current 
B)  the core material 
C)  the spacing of the windings 
D)  the cross-sectional area 
E)  the direction of the current

Question 5

Two parallel wires carrying equal currents of 10 A attract each other with a force of 1 mN. If both currents are doubled, the force of attraction will be:

Accepted Answer

A)  1 mN 
B)  4 mN 
C)  0.5 mN 
D)  0.25 mN 
E)  2 mN 
A)  1 mN 
B)  4 mN 
C)  0.5 mN 
D)  0.25 mN 
E)  2 mN

Question 6

In Ampere's law,   the symbol   is:

Accepted Answer

A)  an infinitesimal piece of the wire that carries current i 
B)  in the direction of   
C)  perpendicular to   
D)  a vector whose magnitude is the length of the wire that carries current i 
E)  none of the above 
A)  an infinitesimal piece of the wire that carries current i 
B)  in the direction of   
C)  perpendicular to   
D)  a vector whose magnitude is the length of the wire that carries current i 
E)  none of the above

Question 7

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length in N/m of one wire on the other is:

Accepted Answer

A)  1 * 10-3, repulsive 
B)  1 *10-3, attractive 
C)  4 * 10-5, repulsive 
D)  4 *10-5, attractive 
E)  none of these 
A)  1 * 10-3, repulsive 
B)  1 *10-3, attractive 
C)  4 * 10-5, repulsive 
D)  4 *10-5, attractive 
E)  none of these

Exam 29: Magnetic Fields Due to Currents

If the magnetic field is uniform over the area bounded by a circle with a radius R, the net current through the circle is:

Which graph correctly gives the magnitude of the magnetic field outside an infinitely long straight current-carrying wire as a function of the distance r from the wire?

A solenoid is 3.0 cm long and has a radius of 0.50 cm. It is wrapped with 500 turns of wire carrying a current of 2.0 A. The magnetic field at the center of the solenoid is:

The magnetic field B inside a long ideal solenoid is independent of:

Two parallel wires carrying equal currents of 10 A attract each other with a force of 1 mN. If both currents are doubled, the force of attraction will be:

In Ampere's law, the symbol is:

Two parallel wires, 4 cm apart, carry currents of 2 A and 4 A respectively, in the same direction. The force per unit length in N/m of one wire on the other is:

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