Unit 12 Basic Electricity and Magnetism

T9. If there were a current flowing of 6 A in a 120-V circuit, what would the resistance be?

20 Ohms.

12. If there were a current flowing of 5 A in a 120-V circuit, the resistance would be?

24 Ohms.

13. If the resistance in a 120-V circuit was 40 Ohms, what would the current be in amperes?

3 Amps.

T10. If the resistance in a 120-V electrical circuit were 30 ohms, what would the current be in amperes?

4 Amperes.

T6. An ampere is

A measure of the quantity of electrons flowing past a point in a given period of time.

4. Describe how a meter would be connected in a circuit to measure the potential difference across a light bulb.

A volt meter would be connected across the terminals of the bulb without interrupting the circuit.

3. State the Differences between AC and DC.

AC - Alternating current is a continually and rapidly reversing current. DC - Direct current travels in one direction.

T12. If a conductor carrying an alternating current were formed into a coil, the magnetic field that is generated

Can be used to open or close switches or valves or perform other useful tasks.

19. What does a forward bias on a diode mean?

Current is flowing in one direction.

7. Ohms law for determining voltage is

E=IR (Voltage = Amps x Resistance)

1. The _______ is that part of an atom that moves from one atom to another.

Electron.

T2. What part of an atom freely moves from one atom to another in a good conductor?

Electron.

T13. A magnetic field can be used to

Generate electricity, operate relays, contactors, and solenoids, and cause electric motors to operate.

T3. Typical insulators are

Glass, rubber, and plastic.

8. Ohms law for determining amperage is

I=E/R (Amperage = Volts / Resistance)

18. Why is it important to use a properly sized wire in a particular circuit?

If a wire is too small for the current passing through, it will overheat, and possibly burn the insulation and cause a fire.

11. Describe the characteristics of the voltage, amperage, and resistances when there is more than one load in a parallel circuit.

In a parallel circuit, the total voltage is applied across each resistance. The amperage is divided between the different loads according to their individual resistances, and the total current is equal to the sum of the currents in each branch. The total resistance is less than the value of the smallest resistance. As more and more resisting paths or branches are added to the parallel circuit, the total resistance or the circuit gets lower and lower.

T8. Loads or power-consuming devices are usually wired

In parallel with each other.

T7. Switches in electrical circuits are usually wired

In series with the load.

T4. Electricity can be produced from

Magnetism, chemicals, and heat.

20. The unit of measurement for the charge a capacitor can store is the

Microfarad.

T15. The unit of measurement for the charge a capacitor can store is the

Microfarad.

T1. What type of charge does an electron have?

Negative.

T14. The primary and secondary windings in a transformer are

Not connected electrically.

T5. The unit of measurement for resistance is the

Ohm.

15. The formula for determining electrical power is

P=EI (Watts = Volts x Amps)

2. When this part of an atom moves to another atom, the losing atom will have a _______ charge.

Positive.

17. What are the three types of opposition to current flow that impedance represents?

Pure resistance, Inductive reactance, and Capacitive reactance.

9. Ohms law for determining resistance is

R=E/I (Resistance = Volts / Amps)

10. Sketch a circuit with three loads wired in parallel.

See figure 12.22. (pg. 289) You do not need the inline ammeter.

16. Describe how a step-down transformer differs from a step-up transformer.

Step-down - More turns of wire in the primary winding than the secondary winding. Step-up - More turns of wire in the secondary winding than the primary winding.

5. Describe how an amperage reading would be taken using a clamp-on or clamp-around ammeter.

The ammeter reads the amps (current) flowing through a single conductor when the clamp is around that conductor.

6. Describe how the total resistance in a series circuit is determined.

The total resistance in a series circuit is determined by how many volts are causing however many amperes to flow in a current. EX: 1 volt / 1 amp = 1 ohm. (E/I=R)

14. Electrical power is measured in

Watts.

T11. What would the voltage be in a DC circuit if there were a current flow of 6 A and a load resistance of 8 ohms?

48 Volts.