Electronics II

Question 1

Direct Current (DC)

Answer 1

An electric current flowing in one direction only.

Question 2

Alternating Current (AC)

Answer 2

An electric current that flows in either direction.

Question 3

Electric current

Answer 3

The flow of electric charge.

Question 4

Electric current equation

Answer 4

I = V / R
or
I = ΔQ / Δt

Question 5

Electric current units

Answer 5

Amperes (A)

Question 6

Potential difference (voltage)

Answer 6

The difference of electrical potential between two points of a component.

Question 7

Potential difference equation

Answer 7

V = I R
or
V = W / Q

Question 8

Potential difference units

Answer 8

Volts (V)

Question 9

Electrical resistance

Answer 9

A measure of the difficulty to pass current through a conductor.

Question 10

Electrical resistance equation

Answer 10

R = V / I

Question 11

Electrical resistance units

Answer 11

Ohms (Ω)

Question 12

Resistors in series

Answer 12

When resistors are connected in series, the current through each resistor is the same.

Question 13

Resistors in series equations

Answer 13

R = R1 + R2 + R3…….

Question 14

Resistors in parallel

Answer 14

The total current through the resistors in parallel, is equal to the sum of the individual currents.

Question 15

Resistors in parallel equation

Answer 15

1/R = 1/R1 + 1/R2 + 1/R3…….

Question 16

Resistivity

Answer 16

A measure of the resisting power of a specified material to the flow of an electric current.

Question 17

Resistivity equation

Answer 17

ρ = R A / L

Question 18

Resistivity units

Answer 18

Ohm-metre (Ωm)

Question 19

Electrical power

Answer 19

The rate, per unit time, at which electrical energy is transferred by an electric circuit.

Question 20

Electrical power equation

Answer 20

P = V I
or 
P = I^2 R
or 
P = V^2 / R

Question 21

Electrical power units

Answer 21

Watts (W)

Question 22

Equation of a complete circuit

Answer 22

ε  =  I R  +  I r
or
ε  =  V  +  I r     
or
ε  =  V  +  v

Question 23

Capactience

Answer 23

The ability of a system to store an electric charge.

Question 24

Capactience equation

Answer 24

C = Q V

Question 25

Capactience units

Answer 25

Farad (F)

Question 26

Energy stored equations

Answer 26

``` W = ½ Q V or W = ½ CV^2 or W = ½ Q^2 / C ```

Question 27

Capacitor discharge equations

Answer 27

``` V = Vo e^ – t / RC or I = Io e^ – t / RC or Q = Qo e^ – t / RC ```

Question 28

Time constant

Answer 28

This is the time taken for the capacitor to discharge to 0.37 of its initial charge.

Question 29

Time constant equation

Answer 29

time constant = RC

Question 30

Potential divider

Answer 30

Consists of two or more resistors connected in series across a source of fixed potential difference.