A shunt-wound DC motor with the field coils and rotor connected in parallel (Figure 1) operates from a 130 V DC power line. The resistance of the field windings, Rf, is 250 N. The resistance of the rotor, R, , is 4.40 2. When the motor is running, the rotor develops an emf E. The motor draws a current of 4.50 A from the line. Friction losses amount to 50.0 W.

What direct current in A will produce the same amount of thermal energy, in a particular resistor, as an alternating current that has a maximum value of 7.2 A?

The motor in a toy car operates on 6.00 V, developing a 4.70 V back emf at normal speed. If it draws 3.00 A at normal speed, what current (in A) does it draw when starting? ____________  A

Most household power in North America is 120? alternating current (VAC). However, some high-power appliances such as electric ranges and clothes dryers typically require a special 220?circuit. In this problem, you will calculate the energy, power, and current required by a dryer. You will also compare different methods of storing the energy required to run this appliance in a typical drying cycle. Consider a dryer that operates on 220?electricity, and it consumes an average power of 3000?. For this homework, the “Alternating Current” part of the story is irrelevant, so please use our ordinary DC equations (Perhaps this dryer has been specially made for physics experiments so it has a second input that allows it to operate on DC voltage as well!) A cubic meter of “natural gas” (mostly methane) at atmospheric pressure contains about40?? of usable energy. How much natural gas (in m3) would it take to power the dryer for 30minutes? Do some googling, and make an estimate (that means getting…