StAIR Design

E V I R A R Electrical TermsNo, thats not itRemember that resistance and amperage are like a teeter totter.

VoltageVoltage is the electromotive force or pressure that pushes the electrons through a circuit. Without pressure electrons can not flow. As a battery dies, it gets weaker until it gets to the point there is not enough pressure to operate the load, i.e. the low battery warning on your cell phone or laptop. A completely dead battery has zero volts.

Lets compare an electrical circuit to a water system. In order for the water to flow, a pump has to push the water through the system just as voltage pushes electrons through a circuit.

Amperage Amperage is the flow of electrons through a circuit. The current is pushed through the circuit by the pressure of the voltage.

The pump pulls water from the well and pushes it on to the faucets. Water flows in the pipes, out the faucets and back into the ground. Electrical current flows in wires just as water flows in pipes.

Resistance Resistance restricts the flow of electrons. The more resistance in a circuit the less current flow. The less resistance in a circuit the greater the current flow.

Resistance affects the flow of electrons just as a faucet controls the flow of water. Turning the handle changes the amount of water flow.Changing the resistance in a circuit changes the current flow.

Check your knowledgeWhat pushes electrons through the circuit?

Voltage

Current

Resistance

Check your knowledgeWhat restricts the flow of electrons?

Voltage

Current

Resistance

Ohm's LawOhms Law is a mathematical relationship between the pressure in voltage, the current flow in amperage and the resistance of a circuit.

Ohm's Law

E=IxRI=E/RR=E/IE = VoltageI = AmperageR = Resistance

Applying Ohms Law When you are diagnosing electrical problems on a vehicle, you need to have a good understanding of Ohms Law. Circuits are affected by changes in voltage, amperage and resistances and therefore affecting the operation of vehicle components.

Voltage Vehicle battery voltage will be around 12.6 volts with the engine off and increase to 13.5 to 14.5 volts when running. If the battery voltage is low and resistance of a circuit is correct, the amperage will also be low and vehicle accessories will not operate properly. Remember to check the battery voltage before testing the rest of the circuit. Service or replace the battery as needed. If battery voltage is correct and the faulty circuit is still malfunctioning, there probably is abnormally high resistance in the circuit.

Resistance vs. Amperage

AWhen resistance goes up,amperage goes down.AWhen resistance goes down, amperage goes up.

Resistance

Amperage

The more resistance , the less the amperage or current flow.The less resistance, the higher the current flow.

Amperage testsMany components have a rated amperage based on their resistance.An amperage test can be made to determine if the resistance is correct. A lower than specification amperage in the circuit showsthere is excessive resistance in the circuit. A higher amperage reading will show there is low resistance in the circuit.

Quiz YourselfWhat is the first thing to test when testing a faulty circuit?

Amperage

Voltage

Resistance

Next Question What happens when corrosion causes the resistance in a circuit to increase?

The amperage increases

The voltage increases

The amperage decreases

You are ready!You have completed this tutorial onelectrical terms and their application.Now you are ready to try some hands on testing!