Electrical Terminology
Potential difference, electromotive force, voltage, current, resistance, conductance, charge, conventional current flow and electron flow.
Electrical terminology, summary notes
- EMF (electromotive force) is the driving force produced by a source, measured in volts. Potential difference (PD) is the voltage dropped across a component.
- Current is the rate of flow of charge: I = Q / t, measured in amperes. One amp is one coulomb per second.
- Resistance R opposes current and is measured in ohms (Ω). Conductance G is its reciprocal, measured in siemens (S).
- Conventional current flows from positive to negative in the external circuit. Electron flow is the opposite, negative to positive.
- ⚠ Exam trap: questions deliberately switch convention. Read carefully whether conventional current or electron flow is being asked about.
- Current
- I = Q / t (amperes)
- Conductance
- G = 1 / R (siemens)
- Charge
- Q = I × t (coulombs)
A charge of 30 coulombs passes a point in 10 seconds. What is the current?
I = Q / t = 30 / 10 = 3 A.
A component has a resistance of 25 Ω. What is its conductance?
G = 1 / R = 1 / 25 = 0.04 S.
Terminology concept map
Electrical Terminology
Electrical terminology quiz
Electrical Terminology, quiz
1. A charge of 30 coulombs passes a point in 6 seconds. The current is:
5 A180 A0.2 A2. A device does 240 joules of work moving 20 coulombs of charge. The voltage is:
12 V4800 V0.083 V3. Conventional current in a circuit is defined as flowing from:
Positive to negative in the external circuitNegative to positive inside the sourceThe same direction as electron drift4. A charge of 30 coulombs passes a point in 10 seconds. The current is:
3 A300 A0.33 A5. The unit of conductance is the:
SiemensOhmCoulomb6. A component of 25 Ω has a conductance of:
0.04 S25 S2.5 S7. The difference between EMF and potential difference is that EMF is:
The driving force produced by the sourceAlways smaller than the PDMeasured in amperes8. One ampere is equal to:
One coulomb per secondOne volt per ohm-secondOne joule per coulomb9. Electron flow in a conductor is from:
Negative to positivePositive to negativeBoth directions equally10. A current of 2 A flows for 5 seconds. The charge transferred is:
10 C2.5 C0.4 C11. Resistance is measured in:
OhmsSiemensVolts12. Potential difference is best described as:
The voltage dropped across a componentThe total EMF of the sourceThe rate of flow of charge