PS-6.6

Explain the relationships among voltage, resistance, and current in Ohm’s law.

Key Concepts:Voltage: volt

Resistance: ohmCurrent: amp

Ohms law

Voltage Voltage occurs because of difference in charge between two points. This is electric potential energy. The symbol for voltage is “V”.

Voltage is sometimes referred to as electrical force. Voltage is the force like quantity that can move electrical charge from one point to another.

Voltage is created by a chemical cell when it changes chemical energy to electrical energy

The acid electrolyte reacts with the Zinc metal releasing electrons.

When a wire connects the terminals of a battery then the voltage will push and pull electrons through a conductor.

Electrons in the wire are pushed by the negative terminal and pulled by the positive terminal through the wire.

A generator changes mechanical energy to electric energy.

When a wire connects the terminals of a generator then the voltage will push and pull electrons through a conductor.

In all devices that produce electrical current, one terminal has extra electrons, thus a negative charge. The other terminal has a deficit of electrons and thus a positive charge.

Electric current:…is the flow of electrons through a conductor

is measured in amperes sometimes referred to as “amps”. The symbol is (A).

1 ampere of electrical current is equal to 6.25 x 1018 ( a coulomb) electrons moving through a circuit in one second!

REALITY CHECK: If you had 1 coulomb of sand grains you would need all these dump trucks to hold them!

Resistance: …happens when the electrons flowing through the wire continually run into things ( in this case copper atoms) in the wire and bounce around.

…Resistance opposes the flow electrons through a conductor. The electrical resistance is like electrical friction… it produces heat!

ELECTRICAL RESISTANCE: …will slow the flow of current because it is harder for the current to get through the conductor.

Wires that have a larger diameter have less resistance. Longer wires have greater resistance.

Electric devices provide much of the resistance in a circuit

Ohms law describes the relationship between voltage, current, and resistance.

The voltage is the product of the current and resistance. (V = I R)One volt will pull one amp of current through one ohm of resistance.

*** EXAMPLE:What is the current in a 12V circuit with a resistance of 200 Ohms?

I=V/RI= 12V / 200 OhmsI= .06ANote: The letter I represents electrical current in Amperes in the equation.

If the voltage increases and the resistance remains the same the current will increase.

If the voltage stays the same and the resistance increases then the current will decrease.

The End….

For Now.…