Electricity

Question 1

What is the Symbol and Units of Charge?

Answer 1

Symbol: Q
Units: Coulombs (C)

Question 2

What is the Charge of an Electron?

Answer 2

-1.6x10^-19 C

Question 3

What is the definition of Current?

Answer 3

Rate of change of Charge
Or
The amount of charge flowing in one second

Question 4

What is the Symbol and Units of Current?

Answer 4

Symbol: I
Units: Ampere (A which is Cs^-1)

Question 5

What is Potential Difference?

Answer 5

The work done per coulomb of charge

Question 6

What is the definition of Current as an equation?

Answer 6

Current = Charge/Time
I = ΔQ/Δt

Question 7

What is the Symbol and Units of Potential Difference?

Answer 7

Symbol: V
Units: Volts (V which is JC^-1)

Question 8

What is the defintion of Potential Difference as an equation?

Answer 8

Potential Difference = Work Done/Charge

V = w/Q

Question 9

What is an alternative name of Potential Difference?

Answer 9

Voltage

Question 10

What is the definition of Resistance?

Answer 10

The ratio of p.d to current

Question 11

What is the Symbol and Units of Ressistance?

Answer 11

Symbol: R
Units: Omhs (Ω which is VA^-1

Question 12

How do you calculate the number of Electrons required to make a Charge?

Answer 12

Number of Electrons = Charge/Electron Charge

n = Q/e (n = 1.6x10^-19)

Question 13

What equation links Power, Energy and Time?

Answer 13

Power = Energy/Time
P = E/t

Question 14

What equation is used to convert between kWh and J?

Answer 14

Joules = Kilowatt x Number of Seconds in a Hour
J = kWa x 3600

Question 15

What set of equations link Power, Potential Difference, Current and Ressistance?

Answer 15

Power = p.d x Current = Current² x Ressistance = p.d²/Ressistance
P = VI = I²R = V²/R

Question 16

What is an Ohmic Conductor?

Answer 16

A conductor where the p.d across it directly proportional to the current

Question 17

What is the Operating Voltage of a Diode?

Answer 17

The p.d which the diode occupies

generaly about 7V

Question 18

What happens to most Conductors when the temperature increases?

Answer 18

The resistance increases

Question 19

Why does Resiatance increase with temperature?

Answer 19

Increased lattice vibration due to more energy
∴ elctrons find it harder to flow
∴ resistance increases

Question 20

What is Superconductor?

Answer 20

A material that when at or beneath the resistance becomes Zero
(Not just close to Zero, But is Zero)

Question 21

What is a use of Superconductors?

Answer 21

MRI scanners

conductors when a very large magnetic field is needed

Question 22

What is a Semiconductor?

Answer 22

A materials whose resistance decreases as temperature increases

Question 23

How does a Semiconductor work?

Answer 23

The temperature increase causes an increase in “free” electrons
∴ more charge is available
∴ resistance decreases

Question 24

What is a Thermistor?

Answer 24

An electrical component that is based on semiconductors

Temp↑ cause Resistance↓

Question 25

How is Current spread out in a Series Circuit?

Answer 25

Current is the same at all points within the circuit

Question 26

How is p.d spread out in a Series Circuit?

Answer 26

It is the product of the current and the resistance of that component.

Question 27

How is the total p.d of a Series Circuit calculated

Answer 27

V(total) = ΣV(components)

Question 28

How is the total Resistance of a Series Circuit calculated?

Answer 28

R(total) = ΣR(compoents)

Question 29

What is the Potential Divider equation?

Answer 29

V(1) / V(total) = R(1) / R(total)

Question 30

How is the Current spread out in a Parallel Circuit?

Answer 30

Current in each branch is based of its resistance

Question 31

How is the total Current in a Parallel Circuit calculated?

Answer 31

I(total) = Σ I (of each branch)

Question 32

How is the total Resistance clalculated within a Parallel Circuit?

Answer 32

1/R(total) = 1/ΣR(of each branch)

Question 33

How is p.d spread out within a Parallel Circuit?

Answer 33

p.d is the same across every branch of the circuit

Question 34

What is a quick way of calculating the total Resistance of identical resistors in parallel?

Answer 34

Total Resistance = Resistance / Number of Resistors | R(total) = R/n

Question 35

What is the Symbol and Units of Resistivity?

Answer 35

Symbol: ρ Units: Ωm

Question 36

What is the equation of Resistivity?

Answer 36

``` Resistivity = Resistance x Cross-Sectional Area / Length ρ = RA/L ```

Question 37

What is the Symbol and Units of Electromotive Force?

Answer 37

Symbol: ε Units: V

Question 38

Define E.M.F?

Answer 38

The p.d of a supply when no current is being drawn

Question 39

What is the Symbol and Units of Internal Resistance?

Answer 39

Symbol: r Units: Ω

Question 40

What is Internal Resistance?

Answer 40

The resistance of a power supply

Question 41

What is Load?

Answer 41

AKA External Resistance | The resistance outside of a power supply

Question 42

What is the equation of E.M.F?

Answer 42

E.M.F = Current (Internal resistance + external resistance) ε = I x (R+r) Or E.M.F = p.d across load + (Current x Internal Resistance) ε = V+Ir

Question 43

What happens if a circuit has a small load?

Answer 43

A large curent will be drawn The p.d lost on intenal resistance will be large p.d supplied to load will be a lot less than the E.M.F

Question 44

What is Kirchoff's First Law?

Answer 44

The sum of the currents at a point is equal to Zero Or Total current in is equal to total current out

Question 45

What is Kirchoff's Second Law?

Answer 45

The sum of the E.M.F is equal to the sum of the p.d around a closed loop Or The total E.M.F provided is equal to the p.d across the components within a closed loop

Question 46

What is a Rheostat?

Answer 46

A resistor where resistance is mechanically changed, by moving the point of contact allong it. It is made of a long coil of wire

Question 47

What is an LDR?

Answer 47

A resistor where resistance is based of light intensity. | Light Intensity↑ cause Tesistance↓

Question 48

What is a potential divider circuit?

Answer 48

a simple circuit that uses resisters(or thermistors,rheostats or LDR's) to supply a variable potential difference

Question 49

What does a potential divider circuit look like?

Answer 49

Look in work book