DC Theory Level V #2

The Superposition Method is based on the fact that the current at any point in a circuit is the sum of the currents caused by each of the power sources

• true

• false

Graphite is an example of a diamagnetic material.

• true

• false

Anytime a conductor cuts through magnetic lines of flux ______.

• it becomes properly polarized

• voltage is induced into the conductor

• creates a series circuit

• free electrons are released

Select all that apply:

The left hand rule for generators can be used to find...

• thrust

• field

• voltage

• current

The ______ in a DC generator changes alternating voltage into direct voltage.

• core

• slip ring

• coil

• commutator

You are asked to install an intercom system at the front gate of Chad's house. The unit to be located at the gate operates on 24 volts, ± 1 volt, and draws 0.5 amps. The power supply is located in the master unit, 500 feet away. What is the smallest copper wire (in cmil) you can use to run this circuit? Given: K_copper = 10.4

• 2700 cmil

• 3000 cmil

• 4760 cmil

• 5200 cmil

One form of Kirchhoff's Law states that the algebraic sum of the _____ in a closed circuit must equal zero.

• resistors

• power sources

• voltage drops

• wattages

A 120 volt kitchen circuit is rated for 20 amps. A microwave oven rated at 1.2 kW and a 500 watt toaster are connected to the circuit. If you add a coffee maker rated at 650 watts and run all of these appliances at the same time, how much (in amps) will this circuit be overloaded? (Breakers cannot be loaded more than 80% of their rated value.)

• 2 amps

• 3.58 amps

• 14.38 amps

• 17.53 amps

In a generator, maximum positive voltage is induced at _____ degrees of armature rotation and maximum negative voltage is induced at ____ degrees

• 0 / 180

• 0 / 360

• 90 / 270

• 180 / 360

A customer asks you to install an attic vent fan powered by a 110 volt, 1/2 hp motor and wants you to tell him approximately how much it will cost him to operate it per day. Power in his area costs about seven and a alf cents per kilowatt hour.

• $0.67 per day

• $0.0584 per day

• $2.30 per day

• $1.50