1. Amperes, Volts and Ohms

2. We use different units to measure different things: We use different units to measure different things: Time – minutes Time – minutes Weight – Kilograms Weight – Kilograms Length – Meters Length – Meters There are special units to measure electricity too!!!! There are special units to measure electricity too!!!! Three of the most important ones are: Three of the most important ones are: Ampere, volt and ohm Ampere, volt and ohm

3. Ampere The size of an electric current depends on how many electrons pass a point in a circuit every second The size of an electric current depends on how many electrons pass a point in a circuit every second The greater the number of electrons, the larger the current The greater the number of electrons, the larger the current Fewer electrons mean a smaller current Fewer electrons mean a smaller current The size of an electric current is measured in amperes (amps) The size of an electric current is measured in amperes (amps) We can say that “ampere” is another name for electric current We can say that “ampere” is another name for electric current

4. Volt Nothing moves by itself Nothing moves by itself A force is needed to make something move A force is needed to make something move Electricity needs a force to move it Electricity needs a force to move it Electrons move in a circuit because a force pushed them Electrons move in a circuit because a force pushed them The name for the force or pressure that pushed electrons is electromotive force The name for the force or pressure that pushed electrons is electromotive force It is often called EMF It is often called EMF The strength of the EMF is measured in volts The strength of the EMF is measured in volts

5. OHM Ohms measure the resistance to the flow of electrons. You know that a wire resists the flow of electrons Ohms measure the resistance to the flow of electrons. You know that a wire resists the flow of electrons The amount of resistance is measured in ohms The amount of resistance is measured in ohms

6. There is a connection between amps, volts and ohms. There is a connection between amps, volts and ohms. When one changes, there must be a change in one or both of the others. When one changes, there must be a change in one or both of the others. There is a rule for figuring out these changes. There is a rule for figuring out these changes. It’s called: OHM’s LAW It’s called: OHM’s LAW

7. OHM’s Law Ohm’s law defines the relationships between power (P), voltage (E), current (I) and resistance (R) Ohm’s law defines the relationships between power (P), voltage (E), current (I) and resistance (R) One ohm is the resistance value through which one volt will maintain a current of one ampere One ohm is the resistance value through which one volt will maintain a current of one ampere