Electronics Basics: Voltage Is Not Current

Keep volts, amps and energy transfer separate.

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Voltage is an energy difference per unit charge between two points, measured in volts. Current is the rate charge passes a point, measured in amperes or amps. For steady current, I = charge / time. These are different quantities, not two names for electricity. Use diagrams and calculations only. Never use wall outlets, short batteries, open powered equipment or handle charged capacitors.

Worked example

A 3 V source transfers 3 J of energy per coulomb of charge in the ideal model. If 2 C passes a point in 4 s, current is 0.5 A. A voltage can exist across an open gap with no steady current.

Voltage is energy per unit charge between two points: three volts means three joules per coulomb. Current is charge per time through a point: two coulombs in four seconds gives half an amp.

Would you believe it?

Conventional current uses the direction positive charge would move. In metal wires, negatively charged electrons drift in the opposite direction.

OpenStax: electrical current

Question 1 Which quantity is measured in volts? Current Time Voltage

Question 2 Which quantity is measured in amps? Resistance Current Voltage

Question 3 If 2 C passes in 4 s, what is the steady current? 0.5 A 8 A 2 A

Question 4 At 3 V, how much energy is transferred per coulomb? 0.5 J 12 J 3 J

Question 5 Can an open gap have voltage across it while steady current is zero? Only if voltage means current Yes No

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