Reading Time: < 1 minutePower (
Energy (
Current Electricity: Exploring Resistance, Power, and Circuits in A-Level Science
What Is Current Electricity?
Current electricity is the flow of electric charge through a conductor, driven by a potential difference.
Key Concepts in Current Electricity
Ohm’s Law
The relationship between voltage (
), current (
), and resistance (
):
![\[ V = IR \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-9cd9b14b3c554a0adc9d50972bf367cc_l3.png "Rendered by QuickLaTeX.com")
Power (
) in Circuits
) in CircuitsThe rate of energy transfer:
![\[ P = IV \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-8ce634b70d3d4e38cfc845d332802849_l3.png "Rendered by QuickLaTeX.com")
Other forms:
![\[ P = I^2R \quad \text{or} \quad P = \frac{V^2}{R} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-aa8f707aca5edf0fee8d4f548cef9d33_l3.png "Rendered by QuickLaTeX.com")
Energy ()
)Energy transferred in a circuit:
![\[ E = Pt \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-6b75a4de602304a01aa4a8a76ef67a1a_l3.png "Rendered by QuickLaTeX.com")
Where 
is time (seconds).
Circuit Analysis
Series Circuits
- Total resistance:
Parallel Circuits
- Total resistance:
Applications of Current Electricity
Home Appliances
Devices use current electricity for operation.
Power Grids
Electricity distribution relies on circuits and resistance management.
Medical Devices
Pacemakers and ECG machines depend on precise electrical currents.
Example Problem
A 
battery powers a 
resistor. Find the current and power.
- Current (
): - Power ():
![\[ I = \frac{V}{R} = \frac{12}{4} = 3 \, \text{A} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-6ba479965bb10e3b19c01acf17caf265_l3.png "Rendered by QuickLaTeX.com")
![\[ P = IV = 3 \cdot 12 = 36 \, \text{W} \]](https://skinattuition.co.uk/core/ql-cache/quicklatex.com-dbc246d7643a13c31387e1c613857d05_l3.png "Rendered by QuickLaTeX.com")
Common Mistakes
- Mixing up series and parallel resistance formulas.
- Forgetting to square terms in power equations (e.g.,
). - Neglecting unit consistency (e.g., time in seconds).
).Practice Questions
- A
battery powers two 
resistors in series. Calculate the total resistance and current. - Explain the differences between series and parallel circuits.
- Describe one real-world application of electrical power in medical devices.
battery powers two 
resistors in series. Calculate the total resistance and current.Skinat Tuition | Building Confidence, Inspiring Excellence Globally.