I R V Voltage – Energy lost by the electrons through the circuit. Current – Number of electrons...

I R

V

Voltage – Energy lost by the electrons through the circuit.

Current – Number of electrons moving through the circuit.

Resistance – the ability of a load or resistor to take energy.

● ●

+

-

e-

e-

Load• a resistor that converts energy.

Resistor• lowers energy• removed as heat

KEY WORDSSeries Parallel

• draw simple schematic diagrams

• predict what happens to voltage and current when cells are connected in series or parallel

• compare resistance in series and parallel.

• Connected end-to-end with another – (-) to (+)• Voltage is the sum of the cells in series. • Current produced is same as single cell.

2 - 1.5 volts cells in series = 3.0 volts in the circuit.

Cells in Series

Cells in Parallel• Connected side-by-side – (-) to (-), (+) to (+)• Voltage produced is the same as a single cell.• Current is shared by the cells in parallel.• Cells split the total current – last longer.

Series circuits

• Only ONE path for current to flow. • Electrons pass through every load, resistor or

device before reaching the positive electrode.

• Current is the same at any point in the circuit.

Schematic

Representational

Series circuits

As more resistors are added in series, the overall current in the circuit decreases.

Parallel circuits

• More than one path for current to flow.• Current will vary at points in the circuit.• Current splits at junction between the paths.• Easier the path (less Ω), more current passes.

• Current before and after split is the same.

Schematic

Representational

Parallel circuits

As more resistors are added in parallel, the overall current in the circuit increases.

Voltmeter: • Placed parallel across the circuit• Measures potential drop of the load.

Ammeter:• Placed in series with the circuit.• Measures current traveling through.

Cells in Series Cells in Parallel

Current Similar to a single cell. Current is split by cells.

Voltage Total voltage = sum of voltages.

Total voltage = voltage from single cell

Resistors in Series

• Current is the same through each resistor. • Voltage across each resistor is different. • Total resistance of the circuit equals the added

up values of the individual resistors:

Equivalent resistance of resistors in series :

R = R1 + R2 + R3 + ...

If the values of the three resistors are: R1 = 8 ΩR1 = 8 ΩR1 = 4 Ω

RT = 20 Ω

I = V = 10 = 0.5 A R 20

10 V

Resistors in Parallel

• Current in a parallel circuit splits up.• Voltage across each resistor in parallel is same.• Total resistance of the circuit equals the added up

reciprocals of the resistance values, and then taking the reciprocal of the total:

Equivalent resistance of resistors in parallel:

1 / R = 1 / R1 + 1 / R2 + 1 / R3 +...

If the values of the three resistors are: R1 = 8 ΩR1 = 8 ΩR1 = 4 Ω

1/RT = 1/8 + 1/8 + ¼ = ½

RT = 2 Ω

I = V = 10 = 5.0 A R 2

10 V

Amount of current through each resistor depends on the resistance:

Individual currents can be found with V = IR:I1 = 10 / 8 = 1.25 A

I2 = 10 / 8 = 1.25 A

I3 = 10 / 4 = 2.5 A

Note that the currents add together to 5 A, the total current.

5 Sources of Electrical EnergyPhotoelectric energy – photo electric cells can convert solar energy to electrical energy

Electromagnetic energy – all things release this type of energyIt can be detected if you have the right sensor.

5 Sources of Electrical Energy

5 Sources of Electrical Energy

Chemical energy can make electrical energy- created by a chemical reaction inside the battery

5 Sources of Electrical EnergyPiezoelectric energy into electrical energy

The piezoelectric effect—a material’s capacity to convert mechanical energy into electrical energy

5 Sources of Electrical EnergyThermoelectric energy – a difference in temperature can convert heat energy into electrical energy creating an electric current