CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Internal Resistance and Potential Dividers
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Deformation of Solids
Thermal Physics
Uniform Circular Motion
Simple Harmonic Motion
The Nucleus and Radioactive Decay
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Current, Charge and Potential Difference
Potential difference, power and current
- 3 things to know
- Unit AS 1
Overview
Equation relating potential difference to power and current and volt in terms of power and current.
What you need to know
Answer each one before you reveal it.
A motor operating at 12 V draws a current of 2.5 A for 5.0 minutes. Calculate the electrical energy supplied.
Show that the watt is equivalent to the volt ampere.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State the equation relating potential difference to power and current, and define every symbol with its unit.
Model answer
The equation is V = P/I, where V is the potential difference in volts, P the power in watts and I the current in amperes; rearranged it gives P = VI.
- 2
Show how V = P/I follows from V = W/Q and I = Q/t.
Model answer
Power is energy per unit time, P = W/t, and substituting W = QV gives P = QV/t; since Q/t is the current I this becomes P = VI, so V = P/I.
- 3
Define the volt in terms of power and current.
Model answer
One volt is one watt of power dissipated per ampere of current, so 1 V = 1 W A⁻¹.
- 4
Calculate the power dissipated when a current of 3.0 A flows through a component with 230 V across it.
Model answer
The power is P = VI = 230 × 3.0 = 690 W, and 690 W ÷ 3.0 A returns the 230 V as a check.
- 5
A lamp is rated 60 W at 230 V. Calculate the current it draws at its rated voltage.
Model answer
The current is I = P/V = 60 ÷ 230 = 0.26 A, and 0.261 A × 230 V gives back 60 W as a check.
- 6
A motor operating at 12 V draws a current of 2.5 A for 5.0 minutes. Calculate the electrical energy supplied.
Model answer
The power is 12 × 2.5 = 30 W, so the energy is 30 × 300 = 9.0 × 10³ J, and 9000 J ÷ 300 s returns 30 W as a check.
Other ways to work this
The same content, four other ways.
What is inside Levo
Six ways to work the same material.
Every question in Current, Charge and Potential Difference, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
Or £46 a year, about £3.83 a month. Cancel anytime.