Power

1. Definition and Key Concepts

• Power $(P)$ is the rate at which energy is transferred or work is done in a circuit.
• Measured in watts $(W).$
• The higher the power, the more energy is transferred per second.

2. Power Formulae

$P = \frac{W}{t} = VI = I^2R = \frac{V^2}{R}$

Where:

• $P =$ Power $(W)$
• $W =$ Work done $(J)$
• $t =$ Time $(s)$
• $V =$ Potential difference $(V)$
• $I =$ Current $(A)$
• $R =$ Resistance $(Ω)$

3. Brightness of Light Bulbs

• The brightness of a bulb depends on the power it dissipates.
• Higher power = Brighter bulb.

Rules for Bulbs in Circuits

1. Bulbs in Series:

• $P ∝ R →$ Bulbs with higher resistance glow brighter.
• Increasing resistance increases power and brightness.

2. Bulbs in Parallel:

• $P ∝ 1/R →$ Bulbs with lower resistance glow brighter.
• Decreasing resistance increases power and brightness. Note: Compact Fluorescent Lights (CFLs) are designed to work with different power ratings and will burn out if the voltage or current is too high.

4. Key Takeaways

• More power = Faster energy transfer.
• Choosing the correct resistance in circuits affects power consumption.
• Understanding power is crucial for designing efficient electrical systems.