In electricity, you typically hear a lot more about amps than about colombs. Voltage and potential Voltage is analogous to hydraulic pressure. The unit is volts , and it's measured by a voltmeter. The metal chassis inside a TV used to be a 120 volt floating ground about half the time, depending on which way you plugged the TV into the outlet. In electricity, you hear a lot more about voltage than potential.
Voltage is an across variable.
You measure the voltage across a resistor, or a capacitor, etc. We will revisit this rule again in the circuit diagrams section. Batteries The power source we will most often use will be a battery - a constant voltage source. A battery has a rating indicating how many volts it supplies. Each battery has a positive terminal and negative terminal clearly marked.