Electrical circuits

Question 1

What is current defined as?

Answer 1

the rate of flow of charge (electrons)

Question 2

The current can be calculated from the expression….

Give it’s rearrangement as well.

Answer 2

Q = It (Charge (C) = Current (A) x Time (s)

Rearrangement:
I = Q/t

Question 3

1 Amp is the same as …

Answer 3

1 Coulomb per second

Question 4

Which way does current flow in a circuit and what is the name of this current?

Answer 4

Current flows from the +ve terminal to the -ve terminal

This is called ‘Convectional current’.

Question 5

Which way do electrons flow in a circuit?

Answer 5

Front the -ve terminal to the +be terminal.

Question 6

What happens to the current and resistance of a circuit with a bulb in series, when another bulb is added?

Answer 6

The current decreases as it is shared between the two bulbs. Therefore the resistance has increased.

Question 7

Show the rules for current in a series circuit.

Answer 7

Current (in) = Current (out)

I1 = I2 = I Total

Question 8

Name the rules for current in a parallel circuit.

Answer 8

A1 = A2 + A3 = ATotal

I1 = I2 + I3

Question 9

What’s the formula for Resistance when it is involving potential difference and current.

Answer 9

R = V/I Resistance (Ohms) = P.d (V) / Current (A)

Question 10

What effect does resistance have on current?

Answer 10

As resistance increases, current decreases which means the flow of charge is reduced.

Question 11

Was does resistance affect in terms of current?

Answer 11

Resistance is the variable that affects the flow of charge and provides a resistive force to that flow.

Question 12

What is potential difference?

Answer 12

Voltage or potential difference (p.d) is the energy (electrical) delivered from the power supply to the component (s), per coulomb of charge.

Question 13

What is energy measured in?

Answer 13

Joules / J

Question 14

What is charge measured in?

Answer 14

Coulombs / C

Question 15

1 Volt =

Answer 15

1 J/C

Question 16

In the required practical ‘Resistance of a wire’ what is resistance directly proportional to?

Answer 16

The length of the wire. i.e. if the length of the wire doubles the resistance doubles

Question 17

What is an IV Graph?

Answer 17

Graph designed to show relationship between current (I) and potential difference (V) for a component.

Question 18

What does the IV graph for a filament lamp show?

Answer 18

It shows that as current increases, p.d increases. However, they are not directly proportional. Current also increases but at a different rate.

Question 19

What does gradient equal in terms of the filament lamp IV graph?

Answer 19

gradient = I / R or R = I / grad.

Question 20

What does the IV graph for a fixed resistor show?

Answer 20

The graph shows a directly proportional relationship between current and p.d. It obeys Ohms law.

Question 21

What does the IV graph for a diode show?

Answer 21

The graph shows that current flows through a diode`in only one direction, when the terminals are reversed, through a p.d is measured, there is no current.

Question 22

In the IV graph for a diode how does resistance affect current?

Answer 22

Resistance to current is high when The resistance is increasing. But the resistance is low when the current increases.

Question 23

In a series circuit what are the rules for current, potential difference and resistance?

Answer 23

ITotal = I1 = 12

VTotal = V1 + V2

RTotal = R1 + R2

Question 24

In a parallel circuit what are the rules for current, potential difference and resistance?

Answer 24

ITotal = I1 + I2

VTotal = V1 = V2

1 / RTotal = 1 / R1 + 1 / R2

Question 25

What is the formula for potential difference in terms of energy and charge?

Answer 25

Potential difference = Energy (J) / Charge (C)

V = E / Q

Question 26

What is the definition of power?

Answer 26

Power is defined as the rate of doing work.

Question 27

What is the formula for power in terms of potential difference and current?

Answer 27

P = VI

Question 28

What is and LDR?

Remember that…

Answer 28

A light dependent resistor

As light intensity increases, resistance decreases.

Question 29

With the practical of the circuit with the wire in room temperature water why is it in water at room temperature?

Answer 29

Water at room temperature prevents temperature increasing by a large.