9702 · 9.2
Potential difference and power
Potential difference (voltage) is like the 'push' given to each unit of charge, telling us how much energy it gains or loses. Power then describes how quickly this electrical energy is being moved or converted into other forms.
Need to know
What you need to know
- 9.2 Potential difference and power.
- Potential difference is defined as the work done to transfer one unit of charge across two points of different potential (charge). 𝑉 = 𝑊 𝑄.
- Here V is the potential difference in volts (V), W is the work done in joules and Q is the charge in coulombs.
- Recall that power is the rate of work done or rate of energy transferred i.e. 𝑃 = 𝑊 𝑡.
- Depending on the info given in the question, the above equation can be written in many forms e.g. 𝑃 = 𝑄𝑉 𝑡 𝑃 = 𝑉𝐼 𝑃 = 𝐼 2 𝑅.
Explanation
The 'Push' and 'Speed' of Electricity
- **Define the 'Push':** Potential Difference (V) measures the energy transferred per unit charge.
- **Define the 'Speed':** Power (P) measures the rate at which energy is transferred or dissipated.
- **Connect Them:** Electrical power is the product of potential difference and current ($P = VI$).
- **Calculate Total Energy:** Total electrical energy is power multiplied by the time it's transferred ($E = Pt$).