1. Homework No. 7 Electric Motor (pg. 1 of 2) Name_______________________
Circle (T) for TRUE or (F) for FALSE or circle the correct selection.
An electric motor converts electrical energy into mechanical energy T------F
The output power of electric motors is usually in the form of a rotating shaft T------F
A force is always exerted on a rotor-coil passing through a magnetic field T------F
The forces exerted on the rotor-coil in an electric motor cause it to rotate T F
Reversing the direction of current flow in a rotor coil will reverse the direction of rotor rotation.-----T F
Reversing the magnetic field polarity has no effect on the rotor direction of rotation T F
The three vectors F, I and B are always perpendicular to each other in the presence of a magnetic field and a wire carrying electric T F
The magnitude of the forces on the rotor coil is proportional to the current flowing through the wires, the magnetic field strength and any length of the wire exposed or not to the magnetic T------F
Electric motors require permanent magnets to 0perate T F
A constant magnetic field sets a stationary electron in motion T F
A strait wire 50cm long conducts a current of 4.0 A directed vertically upward. If the wire is acted on by a force of 1.0x10-2 N in the eastward direction due to the magnetic field at right angles to the length of the wire, what are the magnitude and direction of the magnetic field? Calculate! A.: _________________________________________________________________________________________
A magnetic field exists in the east-west direction, but it is unknown whether it points east or west. Can you determine the direction of the magnetic field, using a current-carrying wire with a known current direction? Explain! A.:________________________________________________________________________________

2. Homework No. 7 Electric Motor (Pg. 2 of 2)
13. An electric motor converts electrical energy into mechanical energy.  A device that converts mechanical energy into electrical energy is called a ___________ .
     a)  energizer;  b)  generator,  c)  mechanizer, d)  electrolyzer.   Answer: (__)
14. A current carrying wire passing through a magnetic field will experience ____________ .
     a)  a force,  b)  a reversal of current flow;  c)  an increase in current ; d) nothing;   Answer:  (__)
15. The magnitude of the forces on electric motor rotor coil is ___________ __ the current flowing in the wires, the magnetic field strength, and the length of the wire in the magnetic field.
    (a)  independent of   ( b) proportional to (c)  inversely proportional to  (d) always constant regardless of. Answer:  (__)
16. The output power of an electric motor is usually in the form of a(n) _________________ .
    a)  electric field, (b)  magnetic field,  (c)  rotating shaft, (d)  hydraulic pump.
Answer:  (__)
17. We have replicated the scientist’s Faraday demonstration which showed that a changing magnetic field flux through a coil area A can induce electric current inside of the coil.
17.1 What is the name of the Faraday induced effect? or Answer: ____________, ____
17.2 As the rotor coil in an electric motor rotates and its rotating area exposed to the magnetic field changes it induces an opposing electric potential called_____ ____? Answer: ____ ___