A small electric car overcomes a 250 N friction force when traveling 30 km/h. The electric motor is powered by ten 14 V batteries connected in series and is coupled directly to the wheels whose diameters are 50 cm. The 300 armature coils are rectangular, 10 cm by 15 cm, and rotate in a 0.50 T magnetic field.
(a) How much current does the motor draw to produce the required torque?
(b) What is the back emf?
(c) How much power is dissipated in the coils?
(d) What percent of the input power is used to drive the car?