Electricity

Electrical Force

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• An object becomes charged by–Friction–Conduction– Induction

Charging by Friction

Charging by induction.

Charging by conduction.

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Electricity can be described like flowing water.

Potential

Current

Load

Charge is a quantity of electricity.

Charge has the unit coulomb (C).

Switch

Charge flows in an Electric

Circuit.

An electric circuit has 4 parts:

Power Source

Load

Connecting Wires

Switch

Flowing charge is called current. The symbol is I and the unit is the ampere or amp (A).

SIM

– Voltage is a measure of the potential difference between two places in a circuit.

– The unit is the Volt (V).

– Voltage IS Potential Energy!!!

– Voltage IS NOT flowing charge.

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1. Dry Cell Battery

2. Wet Cell Battery

Batteries convert chemical energy into

electrical energy!douglasbattery.com

Power plants use generators to

produce power. This generator is called a turbine.

•120V of AC is available at your house’s wall sockets.•It is more efficient for power companies to send AC to your house, but most electrical devices need DC.•These devices have components inside them that convert AC into DC.

AC/DC

•Direct current (DC) is charge moving in one direction•Alternating current (AC) is charge moving back and forth.

•Batteries produce direct current (DC).•The power company uses electrical generators to produce alternating current (AC).

120V AC

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1.5V DC

9V DC

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Electrical Resistance.– This is when current flow is slowed down.– Current seems to lose energy. Actually, the electrical

energy is converted into heat and/or light.– The symbol is R.– The unit is the ohm ().

Stove Top Burners

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Water Heater Element

Light bulb

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A conductor’s electrical resistance depends on Four Variables.• The length of the conductor.• The cross-sectional area of the conductor.• The material of which the conductor is made.• The temperature of the conductor.

The relationship between voltage, current, and

resistance is V = I · R or Ohm’s Law

V = Voltage

I = Current

R = Resistance

(SIM1) (SIM2)

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Digital Multimeters can measure voltage,

current, resistance, and more.

Electrical Work.• A voltage source does work when releasing charge.• The unit of electrical work is joules (J).

Electrical Power.• The unit of power is called the watt (W).• power = current · voltage

P = I · V

Paying for Electricity.• The electric company charges you based on the

amount of power and the amount of time.• The unit is kilowatt-hour (kW-hr).• 1 kW = 1,000 Watts

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Several things in

our homes consume

electricity.

The hot water heater

uses electricity to heat water.

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Look for this sticker to find out how your

appliance compares to

others that are similar.

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Does it cost more to use a 100-W light bulb for 1 hour or 3 hours?

Does it cost more to use a 100-W light bulb for a 60-W light bulb?

SIM

This meter can usually be found outside our home. It keeps track of the amount of electrical

power that your home uses over time.

It is illegal to tamper with it!!!

Where does electricity come from?

Electricity is not entirely efficient.

Sources

• Bloomfield, How Things Work.

• Krauskopf & Beiser, The Physical Universe. 10th ed.

• Tillery, Physical Science.