# Principles of Technology

## Year End Review: Electrical

### Electrical Force (1:3)

1. What is the Prime Mover in the Electrical System?

2. What are the most common sources of AC and DC current?

3. What is moving in an electrical system?

4. Draw a schematic diagram of a simple circuit and label the 4 main components.

5. Draw a schematic diagram of a 12 volt DC circuit with 2 loads connected in series. Assuming no loss of voltage, label what the voltages will be at each of the loads.

6. Draw a schematic diagram of a 6 volt DC circuit with 2 loads connected in parallel. Assuming no loss of voltage, label what the voltages will be at each of the loads.

### Electrical Work (2:3)

1. What is the basic unit of electrical charge?

2. How many electrons are in 1 unit of charge?

3. A dead 12 volt battery can store 12,000 coulombs of charge. How much electrical work is done to completely recharge the battery?

4. A 12 volt battery does 650 volt coulombs of work. How much charge has it moved?

5. An electrical motor does 1500 N·m of mechanical work while it uses up 1850 joules of electrical energy. What is the efficiency of the motor?

6. A 110 volt electric motor draws a current of 13 amps for 15 seconds. How many coulombs of charge are moved?

7. How much charge is moved by a motor if a current of 17.3 amps operates for 1l.5 minutes?

8. If the above motor operates at 220 volts, how much work is completed in the 11.5 min?

### Electrical Rate (3:3)

1. If a DC motor uses 775 coulombs of charge in 15 seconds, how much current is produced?

2. An AC motor operates at 11 amps for 6.5 min. How much charge flows through the motor?

3. A 220 volt heater is rated at 35 amps. How much charge passes through the heater in 25 min?

4. A sine waveform has a period of 75 sec/cycle. What is the frequency?

### Electrical Resistance (4:3)

1. On four band resistors:

the first band represents

the second band represents

the third band represents

the fourth band represents

2. An electrical circuit with a 12V battery operates a floodlight that has 3.25 A of current flowing through it. Find the resistance of the floodlight.

3. A current of 9.5 A has 25.56 ohms of resistance. What is the voltage?

4. A 12-ohm and a 4700-ohm resistor are connected in parallel to a 12V battery. Find the total resistance (Rtot) of the circuit.

5. A 15-ohm resistor and a 230-ohm resistor are connected in series with a 12 volt battery. Find:

a. the total resistance (Rtot) of the circuit

b. the amount of current (I) through the circuit

c. the voltage difference across the 15-ohm resistor

d. the voltage difference across the 230-ohm resistor

6. Calculate the resistance (in ohms) of a 5.75 meter long piece of aluminum wire (resistivity = 2.824 µ) which has a diameter of 0.25 centimeters.