1. A proton with a speed of 4.5 x 10^6 m/s is observed to travel in a circle of radius 0.22m in a magnetic field. What is the strength of the magnetic field?
A. 2.3 x 10^-2 T
B. 2.1 x 10^-1 T
C. 4.7 T
D. 1.1 x 10^5 T
2. A 56V DC motor draws a 2.0A when running at full speed. If the resistance of the armature is 1.5 ohms, what is the back emf (reverse voltage) at this speed?
A. zero
B. 3.0 V
C. 53 V
D. 59 V
3. An ideal transformer is being designed to change a 640 V AC into 120 V AC. What should be the ratio of the number of turns on the primary coil to the number of turna on the secondary coil?
A. 0.035
B. 0.19
C. 5.3
D. 28