Chapter 1

Question 1

What are resistors?

Answer 1

Electronic components that resist or control the flow of electric currents in electrical appliances and devices.

Question 2

Types of Resistors

Answer 2

• Fixed
• Variable

Question 3

What is a potentiometer?

Answer 3

A type of small variable resistor which can have its resistance value changed with a screwdriver

Question 4

What are resistors used for?

Answer 4

To prevent damage to devices/systems or to ensure they operate within safe limits.

Question 5

What are resistors normally composed of?

Answer 5

Metal and Carbon

Question 6

What happens to heat when a current flows through a resistor?

Answer 6

It dissipates

Question 7

What are capacitors?

Answer 7

Electronic components that store and release electrical energy in a electric field, which preserves voltage

Question 8

What are capacitors used for?

Answer 8

They are used in power supplies to provide a temporary backup of electrical energy and in many devices to stabilise voltage levels.

Question 9

What are inductors?

Answer 9

Electronic components that temporarily store energy in a magnetic field.

Question 10

What does a inductor consist of?

Answer 10

A conducting material such as copper wrapped around a core made from a magnetic material.

Question 11

What is the purpose of inductors?

Answer 11

Inductors store energy in a magnetic field when current flows through their coils. They resist changes in the flow of electric current.

Question 12

Capacitors vs Inductor

Answer 12

Inductors store energy in a magnetic field
Capacitors store energy in a electrical field

Inductors conserve current
Capacitors conserve voltage

Question 13

What is a diode?

Answer 13

Devices that allow electrical current to flow in one direction while blocking it in the other direction.

Question 14

Where are diodes used?

Answer 14

• Power supplies
• DC-to-DC converters
• Power inverters
• Switches in digital logic circuits

Question 15

What are LEDs?

Answer 15

Tiny electric bulbs that use small amounts of
electricity, they emit light when electrical current passes through them.

Question 16

What does LEDs stand for?

Answer 16

Light Emitting Diodes

Question 17

What are Op-amps?

Answer 17

Electronic devices that amplify the difference in voltage between the two inputs (inverting and non-inverting). They make small changes in voltage much larger.

Question 18

What does Op-amps mean?

Answer 18

Operational Amplifier

Question 19

Where are Op-amps used?

Answer 19

In signal amplification

Question 20

What are switches?

Answer 20

Devices that open or close an electrical circuit. When you flip a switch, it either allows electricity to flow through (closed) or blocks it (open).

Question 21

What is Ohm’s law?

Answer 21

Voltage is directly proportional to the current provided R remains constant.

The current is inversely proportional to the resistance provided the voltage remains constant.

Question 22

Mathematical expression of Ohm’s law

Answer 22

Voltage = Current * Resistance or V = I R

Question 23

What is the relationship between current and resistance?

Answer 23

Current is inversely proportional to resistance

Question 24

Symbol and Unit of Voltage

Answer 24

V and Volt

Question 25

Symbol and Unit of Current

Answer 25

I and A (Ampere)

Question 26

Symbol and Unit of Resistance

Answer 26

R and Ω (Ohm)

Question 27

What is voltage?

Answer 27

Electrical pressure that causes charged electrons to flow through a conducting loop, enabling them to do work such as illuminating a light bulb.

Question 28

What are the types of voltage?

Answer 28

* direct (DC) * alternating (AC)

Question 29

What type of polarity does AC and DC have?

Answer 29

DC maintains the same polarity whilst with AC the polarity changes direction periodically.

Question 30

What is polarity?

Answer 30

The direction of the current

Question 31

What is a DC power supply?

Answer 31

An electrical device that is capable of generating a constant voltage that a direct voltage needs.

Question 32

What is the current?

Answer 32

The rate of charged particles (electrons) through an electric circuit

Question 33

How does the electric current flow in a circuit?

Answer 33

The conventional flow of an electric current is from the positive terminal towards the negative terminal of a battery or power supply.

Question 34

How to work out the resistance in a parallel circuit?

Answer 34

1/Rₜ = 1/R₁ + 1/R₂ + 1/R₃ or V/Rₜ = V/R₁ + V/R₂ + V/R₃

Question 35

What is the voltage divider rule?

Answer 35

A way to determine voltage values across resistors when placed in series

Question 36

Equation for the voltage divider rule

Answer 36

V₁ = R₁ / (R₁ +R₂) x Vₜ V₂ = R₂ / (R₁ + R₂) x Vₜ

Question 37

What is the current divider rule?

Answer 37

A method to determine current values through resistors when they are placed in parallel.

Question 38

Equation for the current divider rule

Answer 38

I₁ = (R₂ / (R₁ + R₂)) x Iₜ I₂ = (R₁ / (R₁ + R₂)) x Iₜ

Question 39

When is the current divider rule not used directly?

Answer 39

If the circuit contains more than two resistors in parallel

Question 40

What is Kirchhoff's Current Law?

Answer 40

The sum of the currents flowing through all the wires that meet at a node or point in a circuit is equal to zero. Flowing ways is negative Flowing towards is positive Example. I₁ - I₂ + I₃ + I₄ = 0

Question 41

For Kirchhoff's current law describe how the currents flowing from and away from the node are presented?

Answer 41

The current flowing towards the node is taken to be positive and that flowing away from the node to be negative.

Question 42

What is Kirchhoff's Voltage Law?

Answer 42

The sum of the voltages within any loop in a circuit is equal to the sum of the products of the currents and resistors in the various parts of the loop.

Question 43

Equation of Kirchhoff's Voltage Law

Answer 43

V₁ - I₁ R₁ - (I₁ - I₂) x R₂ = 0 (I₁ - I₂)R₂ - V₂ - I₂R₃ - I₂R₄ - I₂R₅ = 0

Question 44

Define Electrical Power and an example

Answer 44

The rate of change of energy i.e. the change of electrical energy with time.

Question 45

Symbol and Unit of Electrical Power

Answer 45

P and Watt (W)

Question 46

Equation for Electrical Power

Answer 46

P = VI P= I²R P = V² / R