Current Electricity

Current, Power and Energy

Current Electricity

• Current Electricity is what you get when you plug something into the wall.

• There are lots of electrons in one place, but they are moving along wires and through electronic devices.

• That is the difference between static and current electricity.

Voltage

• Voltage: is like the Potential Energy of Electricity. It’s what moves the electrons along.

• Ex: A 9volt battery is what pushes the electrons through a toy car.

• Variable: V Unit: Volt (V)

Current

• Current is how fast electrons are moving through an object (like a TV or a light bulb).

• Variable: I Unit: Ampere (A)• Current in electricity is similar to current in a

river…

Current

• The faster we can move electrons, the more Current (I) we can get.

• Current can be calculated using:

t

QI

Example

• A wire carries 10 Coulombs of charge past a certain spot every 2 seconds. What is the current in the wire?

As

CI

t

QI

52

10

Electric Power

• Electric Power is how quickly an object uses electricity to do work.

• Variable: P Unit: Watt (W)

• Most appliances are rated in Watts to tell you how much energy they use.

Electric Power

• Electric Power can be calculated using the formula:

• Electronics with higher power ratings make your power bill go up!

IVP

Example

• If a 1000W microwave is plugged into a 120V outlet, what kind of current will it draw?

IA

IV

W

VIW

IVP

3.8120

1000

)120(1000

Power Bills

• The power company measures how much power you use in Kilowatts (kW), and they charge by the hour (h).

• THIS IS THE ONLY TIME we’ll use kW and h for our units: when calculating a Power Bill.

Power Bills

• Power Companies charge a certain amount of money per Kilowatt-Hour.

• Your Power Bill comes from:

Amt. of Bill ($) = (rate)(P)(t)

Example

• If you leave your 1500W TV on for a whole day, how much will it cost you if the power company charges 0.008 $/kWh? (Remember 1kW=1000W)

28.0$

)24)(5.1)(/$008(.$

))()(($

hkWKwh

tPrate

Review

• Our three new equations are:

))()(($ tPrate

IVPt

QI

Charge (Q) – Coulombs (C)Current (I)- Amperes (A)Voltage (V)- Volts (V)Power (P)- Watts (W)

Power Bill ONLYPower (P)- Kilowatts (kW)Time (t)- hours (h)