Unit 1: Topic 1: Alternating Current and Voltage

Question 1

What is all matter made up of?

Answer 1

Protons, neutrons and electrons.

Question 2

The _____ charged protons and attracted to the _____ charged electrons.

Answer 2

positively, negatively.

Question 3

What is the overall charge of an atom?

Answer 3

Zero.

Question 4

In an atom, the number of _____ must equal the number of electrons.

Answer 4

protons.

Question 5

What is an electric charge measure in?

Answer 5

Coulombs, C.

Question 6

What is the definition of an electric current?

Answer 6

It’s the measure of the flow of charge around a circuit and depends on the amount of charge passing any point in a circuit every second.

Question 7

What is electric current measured in?

Answer 7

Amperes, A.

Question 8

What is electric charge measured in?

Answer 8

Coulombs, Q.

Question 9

A battery supplies a ____ e.m.f.

Answer 9

Constant.

Question 10

Why does a battery supply a constant e.m.f?

Answer 10

It’s so the current is always in the same direction.

Question 11

What does d.c stand for?

Answer 11

Direct current.

Question 12

What does a.c stand for?

Answer 12

Alternating current.

Question 13

What are transformers essential for?

Answer 13

To step voltages up or down for the transmission of electrical energy.

Question 14

In transformers, less energy is dissipated as heat in the cables when a high ____ and so a _____ current is used to transmit electrical ____.

Answer 14

voltage, smaller, energy.

Question 15

In an a.c supply, what are the maximum values called?

Answer 15

Peak values, Vp.

Question 16

In an a.c supply, the peak to peak values are ___ the peak value, Vpp.

Answer 16

twice.

Question 17

On an a.c waveform, does the e.m.f change amplitude?

Answer 17

Yes, constantly.

Question 18

What is the equation used for the period of a wave?

Answer 18

T=1/f.

Question 19

What is a Cathode Ray Oscilloscope used for?

Answer 19

It’s an extremely versatile device which is used to measure a.c and d.c voltages. It can also measure a.c signals.

Question 20

Voltages to be measured are connected to the _ plates of the CRO which have a _____ gain which affects the Y ______.

Answer 20

Y, variable, sensitivity.

Question 21

When measuring frequency using a CRO, what does the time base control do?

Answer 21

Changes the time which the spot takes to move horizontally across the screen.

Question 22

When measuring frequency using a CRO, what is the time base used for?

Answer 22

To find the frequency of an a.c wave.

Question 23

What is the definition of frequency?

Answer 23

The number of cycles (waves) in 1 second.

Question 24

What is the equation used for frequency?

Answer 24

Frequency = 1/time for 1 wave.

Question 25

What is frequency measured in?

Answer 25

Hertz (Hz).

Question 26

What is time measured in ?

Answer 26

Seconds (s).

Question 27

What does Hz equal too?

Answer 27

s^-1.

Question 28

What is the definition of the rms?

Answer 28

The a.c voltage which produces the same heating effect as a d.c voltage.

Question 29

What does rms stand for?

Answer 29

Root mean squared voltage.

Question 30

What does the word ‘mean’ in rms represent?

Answer 30

Average.