SI base units
Physical Quantities & Units - OCR A-Level Physics
Worked Example [3 marks]
The voltThe SI unit of potential difference and EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V).. One volt is one joule per coulomb. is the unit of potential differenceThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V).. Using the equations V = W/Q and W = Fd, express the voltThe SI unit of potential difference and EMFElectromotive force. The energy transferred per unit charge by a source in driving charge around a complete circuit. Measured in volts (V).. One volt is one joule per coulomb. in SI base unitsThe fundamental units from which all other units are derived: kilogram (kg), metre (m), second (s), ampereThe SI unit of current. One ampere is a flow of one coulomb of charge per second. (A), kelvin (K), mole (mol). Defined by international agreement..
Show Solution
1
Start with $V = W/Q. The unit$ of Q is $C = A s$.
[1]2
$W = Fd, so [W] = [F][d] = (kg $m \(s^{-2}\)$)(m) = kg m^2 $\(s^{-2}\)$.$
[1]3
$Therefore [V] = [W]/[Q] = kg m^2 $\(s^{-2}\)$ / (A s) = kg m^2 $\(s^{-3}\)$ $\(A^{-1}\)$.$
[1]Answer
$1 V = 1 kg m^2 $\(s^{-3}\)$ $\(A^{-1}\)$$