Electricity

Question 1

Current

Answer 1

The rate of flow of charge around a circuit

Question 2

What is current caused by?

Answer 2

The movement of charged particles

Question 3

An ideal ammeter has?

Answer 3

Zero resistance as it would change the current

Question 4

Electrons flow from

Answer 4

The negative terminal to the positive terminal

Question 5

Potential Difference

Answer 5

Work done per unit charge

Question 6

An ideal voltmeter has ?

Answer 6

Infinite resistance

Question 7

Resistance

Answer 7

A measure of opposition to the flow electrons through the component

Question 8

Ohm’s Law

Answer 8

The pd across an ohmic conductor is directly proportional to the current flowing through it provided physical contact do not change

Question 9

The gradient in an IV graph

Answer 9

Resistance = 1/gradient

Question 10

IV characteristics of a resistor

Answer 10

Low resistance = Steep gradient
High resistance = Shallow gradient

Question 11

Resistivity

Answer 11

Measure of how much opposition to the flow of electrons a conductor has

Constant value

Question 12

Equation for resistivity

Answer 12

Resistivity = RA/L

Question 13

The resistance of a wire is….

Answer 13

Inversely proportional to the area and inversely proportional to the length

Question 14

Junction Rule

Answer 14

At any junction in the circuit, the total current entering the junction is equal to the total current leaving the junction

Question 15

Loop rule

Answer 15

For any closed loop in a circuit, the sum of the emfs around the loop is equal to the sum of the potential drops

Question 16

Power

Answer 16

The rate of energy transfer (Watts)

Question 17

Power equation 1

Answer 17

Power = Current x Potential Difference

Question 18

Power equation used in series

Answer 18

P = I^2 x R

Question 19

Power Equation used in parallel

Answer 19

P = V^2/R

Question 20

Variable Resistor

Answer 20

Used to vary the current to a minimum when placed in series to a component

Question 21

Potential Divider

Answer 21

An arrangement of resistors

Question 22

Advantage and disadvantage of variable resistor

Answer 22

Adv - Easy to connect

Dis - Current through a component can never be = 0 - variable resistor is set to it’s max resistance

Question 23

Advantages and disadvantages of potential dividers

Answer 23

Adv - current through the component and Pd can be reduced to 0

Disadv - wastes power

Question 24

Charge is ?

Answer 24

The fundamental property of matter

Question 25

How to calculate the number of electrons in one Coulomb?

Answer 25

1/(charge of an electron) Charge of an electron = 1.6 x 10^-19

Question 26

What can a variable potential divider be used for?

Answer 26

Change the output voltage with a fixed pd of supply

Question 27

Why does the resistance decrease with an increase in temperature in thermistors?

Answer 27

The number of charge carriers increases with an increase in temp as electrons break from from the atoms of the semiconductor Therefore, there is a greater current and the resitance decrease

Question 28

Resistance- temp graph of thermistor

Answer 28

Decrease in resistance as temp increases is non linear Almost like the letter L

Question 29

I/V characteristic of a thermistor

Answer 29

Thermistor with higher temp is steeper Thermistor with lower temp is shallower Constant temp = straight line Higher temp (non constant) gradient increase

Question 30

Resistance of an LDR?

Answer 30

Decreases as light intensity increases Same as thermistor but with light

Question 31

Superconductor

Answer 31

Material with 0 resistivity at and below the critical temperature

Question 32

Superconductivity

Answer 32

Property of superconductors

Question 33

Critical temperature

Answer 33

Temperature at and below which a superconductor has 0 resistivity

Question 34

Superconductors graph Resistance-Temp graph

Answer 34

Straight line going along x axis Shoots up at critical temperature Then slow starts increasing gradient then quickly rises u

Question 35

When the temperature drops to the critical temperature?

Answer 35

The resistivity of the superconductor will suddenly drop to 0

Question 36

Superconductors can be used to make?

Answer 36

High power electromagnets and generate very strong magnetic fields Used in particle accelerators and MRI scanners Expel magnetic fields and repel magnets

Question 37

Electromotive force

Answer 37

Electrical energy per unit of charge produced by the source EMF > Terminal PD

Question 38

Terminal pd

Answer 38

Electrical energy per unit charge that is delivered to external components

Question 39

Internal resistance

Answer 39

Resistance of materials within the battery OR The loss of potential difference per unit current in the source

Question 40

Equation for EMF

Answer 40

EMF = I(R + r) EMF (V) - EMF Force I (A) - Current R (Ohms) - Resistance of components in the circuit r (Ohms) - Internal resistance

Question 41

Other equation for EMF

Answer 41

EMF = V + Ir Where V = terminal PD