Physics 2 Electricity

Current

Current

The rate of flow of charge in a circuit.

What is the relation between current, charge, and time?

I = Q/t

Current = charge/time

What is the unit for charge?

Coulombs (C)

What is the unit for time?

Seconds (s)

What is the unit for current?

Amps (A)

What is the unit for energy?

Joules (J)

Voltage

The energy stored per coulomb of charge.

Potential difference

The difference in energy between two groups of charge.

Electromotive force (EMF)

The energy transferred to the charges by the battery.

State the relation between Voltage, Energy, and Charge.

V = E/Q

Voltage = Energy/Charge

True or false - Voltage can also be called potential difference.

True

True or false - There must be a gap in a circuit for a current to flow.

False

True or false - Electrons carry energy round a circuit.

True

True or false - In a light bulb, electrical energy is transferred into heat and light energy.

True

True or false - Current is measured in volts.

False

True or false - If more electrons start flowing round a circuit, the current gets smaller.

False

State the relationship between Resistance, Voltage, and Current.

Voltage = Current x Resistance V=IR

Resistance = Voltage/Current R=V/I

Current = Voltage/Resistance I=V/R

What is the unit for resistance?

Ohms (Ω)

What does resistance do in a circuit?

Makes it harder for a current to pass through a conductor / Slows the current in a circuit down.

How do you calculate the total resistance for resistors in a SERIES circuit?

Rtotal = R1 + R2 + R3 - So on

What is the Rtotal in this series circuit?

1000 + 470 + 22 = 1492Ω

How do you calculate the total resistance for resistors in a PARALLEL circuit?

(R1 x R2)/(R1 + R2)

What is the Rtotal in this parallel circuit? 3 Sig. Fig.

(220 × 10)/(220 + 10) = 2200 / 230 = 9.57Ω

How do you calculate the total resistance for resistors in a PARALLEL circuit when there are 3 or more resistors?

1/Rtotal = 1/R1 + 1/R2 + 1/R3 and so on.

What is the Rtotal of this parallel circuit? 3 Sig. Fig.

1/100 + 1/33 + 1/560 = 0.01+0.03 + 0.00179 = 0.04179

1/Rtotal = 1/0.04179

Rtotal = 23.9Ω

How do you calculate the equivalent resistance?

1/R1 + 1/R2 so on

Get the same denominator and find the reciprocal.

Power

The rate of doing work.

State the relationship between Power, Energy, and Time.

Power = Energy/Time

P = E/t

What is the unit for power?

Watt (W)

What is 1 Watt?

1 Watt = 1 Joule transferred in 1 second

What is the unit for energy?

Joules (J)

What is the Kilowatt hour?

The energy transferred when a power of 1kilowatt (1000W) is used for 1 hour.

State the relationship between Power, Current, and Voltage.

P = I x V

State the relationship between Power, Current, and resistance.

P = I² x R

State the relation between the 2 power equations.

E = IVt

Energy = Current x Voltage x time

What does the Earth wire do?

The earth wire prevents electric shocks by safely directing excess current to the ground if a fault occurs.

What does the Neutral wire do?

The neutral wire carries current back to the power source to complete the electrical circuit and helps balance the voltage in the system.

What does the Insulation do?

Insulation prevents electrical current from escaping from wires or components, protecting users from electric shocks and preventing short circuits.

What does the Live wire do?

The live wire carries electric current to power devices.

What does the Fuse do?

A fuse is a safety device that breaks an electrical circuit when the current exceeds a certain level, protecting the circuit and preventing damage from overloads or short circuits.

What does the Cable grip do?

A cable grip holds and protects electrical cables.

What is a double insulator?

An electrical device has two layers of protection to prevent electric shock, so it doesn't need to be earthed.

State the relation between power, force, distance and time.

P = (F x d) / t