Chapter 4: Circuit Theories

Question 1

Circuit

Answer 1

A circuit consists of electrical components such as batteries, light bulbs and switches connected together with wires.

Question 2

Source

Answer 2

The battery is the source of EMF to move the charge in the circuit.

The EMF that drives the charge around the circuit.

Question 3

Load

Answer 3

A component which converts electrical energy into other forms such as light, heat or kinetic energy.

Question 4

Closed circuit

Answer 4

Current can flow in a continuous path linking the positive terminal to the negative terminal of a source.

Question 5

Open circuit

Answer 5

Current cannot flow because the path is interrupted or broken.

Question 6

Short circuit

Answer 6

A low-resistance path that is undesirable and harmful.

Question 7

Switches

Answer 7

Use to open and close a circuit

SPST
SPDT

Rating of switches:

• Electric circuit broke -> arc occurs
• Arc depends on voltage or current
• Arching can cause the switch to char and wear off
• Switches have both current and voltage rating
• Exceeding the rating will shorten the lifespan of a switch

Question 8

Overloading

Answer 8

When the current flowing through a wire exceeds the current rating

Question 9

Series

Answer 9

Current:
I_total = I_1 = I_2 = I_3
Voltage:
E = V1 + V2 + V3
Resistance:
R_total = R1 + R2 + R3

Question 10

Voltage

Answer 10

Current:
I_total = I_1 + I_2 + I_3
Voltage:
E = V1 = V2 = V3
Resistance:
R_total = 1/R1 + 1/R2 + 1/R3

Question 11

Voltage Divider Rule (SERIES ONLY)

Answer 11

V1 = R1/R1+R2 x E

Question 12

Resistive Current Divider (PARALLEL ONLY & WORK WITH 2 RESISTORS ONLY)

Answer 12

I1 = R2/R1+R2 x I_total

Question 13

KCL

Answer 13

KCL states that the algebraic sum of all currents entering and leaving the node is equal to 0.

Question 14

KVL

Answer 14

KVL states that the algebraic sum of all voltages in a closed loop is equal to 0.

A closed loop is an electrical path that starts and end at the same point.