P5 - Electricity in The Home

Question 1

What is meant by the term voltage?

Answer 1

The push from a battery.

Question 2

What is voltage an alternative word for?

Answer 2

Potential difference (pd)

Question 3

What are the units and symbol of voltage/potential difference?

Answer 3

Voltage, V

Volts

Question 4

How is voltage measured?

Answer 4

Using a voltmeter.

Question 5

What is meant by the term current?

Answer 5

The flow of electrons and how fast they flow.

Question 6

What is an alternative defitinion of current?

Answer 6

The charger per second.

*think ‘c’ for current and ‘c’ for charge.

Question 7

What are the units and symbol of current?

Answer 7

Current, I (I for intensity)

Amperes/amps (A)

Question 8

How is current measured?

Answer 8

Using an ammeter.

Question 9

What is meant by the term power?

Answer 9

The rate of which energy is transferred per second.

P = E/t

Question 10

What are the units and symbol of power?

Answer 10

Power, P

Watts (w)

Question 11

What is the equation used to calculate the power supplied to an electrical appliance?

Answer 11

Power = Current x Voltage

P = I x V

(W) = (A) x (V)

Question 12

What does charge mean?

Answer 12

The property of a body which experiences force in an electrical field.

Question 13

What sub-atomic particles are ‘charge carriers’?

Answer 13

Electrons

Question 14

What is the symbol and unit of charge?

Answer 14

Charge, Q

Coulombs, C

Question 15

What is the charge of an electron?

Answer 15

1.6 x 10^-19 coulombs

Question 16

How is charge calculated?

Answer 16

Charge = Current x time

Q = I x t

(C) = (A) x (s)

Question 17

What is meant by the term resistance?

Answer 17

Refers to how much the flow of electrons is reduced.

*how much of the push from the battery is effecting the current.

Question 18

What are the units and symbol of resistance?

Answer 18

Resistance, R

Ohm’s (Ω)

Question 19

How do you calculate resistance? Ohm’s Law:

Answer 19

Ohm’s Law:

Resistance = Voltage / Current

R = V / I

(Ω) = (V) / (A)

Question 20

How do you caulculate the energy supplied to a circuit? *Used in RP1.

Answer 20

Energy = Current x Voltage x time

E = IVt

(J) = (A) x (V) x (s)

Working out:
E = Pt
we know P = IV
so E = IVt

Question 21

What is the equation for power supplied to the resistor?

Answer 21

Power to resistor = (current)^2 x resistance

P = I^2 x R

(W) = (A)^2 x (Ω)

Question 22

Why is the power to a resistor equal to I^2 x R?

Answer 22

Combine Ohm’s Law (R=V/I) with P = IV

Substituting V = IR into P=IV gives P = I(IR) = I^2R

P = I^2 x R

Question 23

How do you calculate the energy supplied to a resisitor?

Answer 23

Energy to a resistor = Charge x Voltage

E = *Q x V

(J) = (C) x (V)

*Q = It

So this equation is essentially E = ItV, the same as E = IVt for normal electrical energy.

Question 24

What is the equation for calculating the cost of electricity?

Answer 24

Cost of Electricity = Power x Time x Unit Cost

Pence, p) = (kW) x (hrs) x (pence/kWh

Question 25

What is the unit cost also referred to as?

Answer 25

Tariff - the cost per kilowatt hour (p/kWh)

Question 26

What would the cost of electricity be if 10W of energy is supplied in 24 hours, with a unit cost of 12 pence/kWh?

Answer 26

Cost = P x t x kWh

10 W = 0.01kW

= 0.01kW x 24 x 12 = 2.88p