E V I R A R Electrical Terms

Basic Terms Voltage It is measured in volts and is symbolized with a V for volt or an E for electromotive force. Amperage It is measured in amps and is symbolized with an A for amps or an I for induction. Resistance It is measured in ohms and is symbolized by Ω for ohms or R for resistance.

Voltage Voltage 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 knowledge What pushes electrons through the circuit? Voltage Current Resistance

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

Resistance affects the flow of electrons just as a faucet controls the flow of water. The pump pushes the water. What pushes the current? No, that’s not right

You are correct! The electrons are pushed by voltage. Voltage pushes the electrons through a circuit just as a pump can push water through a pipe.

Check your knowledge What is the flow of electrons called? Voltage Current Resistance

That’s not correct Voltage is the electromotive force or pressure that pushes the electrons through a circuit. Without pressure electrons can not 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. No, that’s not right

You are correct! The flow of electrons is called current, just like the current is the flow of water in a river.

Check your knowledge What restricts the flow of electrons? Voltage Current Resistance

That’s not correct Voltage is the electromotive force or pressure that pushes the electrons through a circuit. Voltage pushes electrons rather than restrict them.

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

You are correct! Resistance in a circuit affects current flow just as a faucet affects water flow. You got them all right. Good Job!

Ohm's Law Ohm’s 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=IxR I=E/R R=E/I E = Voltage I = Amperage R = Resistance

Applying Ohm’s Law When you are diagnosing electrical problems on a vehicle, you need to have a good understanding of Ohm’s 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 Ω A When resistance goes up, amperage goes down. A Ω When 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 tests Many 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 shows there is excessive resistance in the circuit. A higher amperage reading will show there is low resistance in the circuit.

Quiz Yourself What is the first thing to test when testing a faulty circuit? Amperage Voltage Resistance

Not Yet! Amperage tests are used to determine resistance of a circuit. Not yet, but soon. Try again.

Not Quite Resistance can definitely be a problem, but you should check something else first.

You are correct! Check the battery voltage first. If the voltage is low then your amperage readings will not be accurate.

Next Question What happens when corrosion causes the resistance in a circuit to increase? The amperage increases The voltage increases The amperage decreases

No, that’s not it Remember that resistance and amperage are like a teeter totter.

Try again The battery voltage generally remains the same. Resistance affects amperage or current flow.

Congratulations Resistance and amperage are like a teeter totter. When resistance increases, amperage decreases. and when resistance drops the amperage increases.

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