NOTES 17 - Circuits

What is a circuit?•Circuit – a pathway for electric current to travel through

What is a circuit made of? • Circuits are made up of

devices called components

• Components are things like light bulbs, switches, wires, and resistors

• A circuit needs a voltage source to make current flow

• Voltage source could be a battery, a solar panel, or an outlet

How does a circuit work?

• Electric current flows from the voltage source through the components and back to the voltage source

• When the electrons leave the voltage source they have high potential energy

• As the electrons flow through the circuit they give their energy to the components they flow through

How does a circuit work?

• They return to the voltage source with low potential energy

• The voltage source reenergizes the electrons before they flow back out through the circuit

What does a circuit do?

• A circuit uses the energy of the moving electrons to do work

• Electrons light up light bulbs when they flow through the filament

• They make electric motors spin to run fans, and refrigerator compressors

• They make speakers vibrate to produce sound

What is a closed circuit?

• Closed Circuit – a circuit that allows current to flow, there is no break in the path (switch is on)

• Switch – interrupts the flow of charges by opening or closing a circuit

What is an open circuit?

• Open Circuit – circuit with a break in the path somewhere, so current flow gets blocked and things won’t work (switch is off)

What is the difference between a series circuit & a parallel circuit? • Series Circuit –

circuit with a single path for current

• Parallel Circuit – circuit with multiple paths for current

Series Parallel

• If any part is removed or broken, the whole thing will not work

• If one bulb breaks the others won’t work

• If one path is broken, the other paths will still work

• If one bulb breaks the others still work

What is a fuse?• Fuse – a metal

strip that protect circuits from overloading

• The metal strip melts when too much current flows

• EX. A 13 amp fuse melts at 13 amps of current

What is a circuit breaker?

• Circuit Breaker – A switch that opens a circuit automatically when the current exceeds a certain value.

What is electric power?

• Electric Power – the rate at which electrical energy is used in a circuit

• Power = current x voltage P = I x V

• Power is measured in watts (W)

• A kilowatt (kW) is 1000 watts

• What’s a megawatt?– 1 million watts

How is electricity usage measured?

• A meter is attached to the lines entering your house

• Every electrical appliance uses a certain number of kilowatts every hour (kWh)

• The meter counts the total number of kWh and the electric company multiplies that by the price per kWh and sends you a bill

• Cost 5 to 20 cents per kWh

Sample savings for replacing an old 22 c.f. fridge with a newer model

A 22 cf fridge made in this year...

Uses about thismuch energy...

Replacing with a2001+ model saves:

Replacing with a 2008+

Energy Star model saves:

Replacing with aCEE Tier 3 model

saves:

<1976 2200 kWh $238 / yr. $257 / yr. $266 / yr.

1976-86 1700 kWh $165 / yr. $183 / yr. $192 / yr.

1987-89 1150 kWh $83 / yr. $101 / yr. $110 / yr.

1990-92 1100 kWh $73 / yr. $92 / yr. $101 / yr.

1993-00 850 kWh 37 / yr. $55 / yr. $64 / yr.

2001-2010 600 kWh - $18 / yr. $28 / yr.

2001-2004 Energy Star (10%+ better)

550 kWh - $9 / yr. $18 / yr.

2004-2008 Energy Star (15%+ better)

525 kWh - $5 / yr. $14 / yr.

2008-2010 Energy Star (20%

+ better)

500 kWh - - $9 / yr.

CEE Tier 3 (30%+better)

425 kWh - - -

Bold rows are current models.  Assumes electricity rate of $0.15 per kWh and icemaker OFF.

Want to save money on electricity?

1. Use less (turn off lights, appliances when not in use, etc.)

2. Think about efficiency when purchasing electrical devices