How to play Bulb Brightness
- Choose a test and read the bulbs and the supply on the card.
- Use P = V·I, P = I²·R, or P = V² ÷ R; turn a rating into a resistance with R = V² ÷ P.
- Type your prediction and press Start. The supply rises and each bulb glows with its own power.
- Compare the wattmeters and the bars with your orange prediction.
Electrical power
Power is how fast electrical energy is turned into light and heat, measured in watts (joules each second): P = V·I. With Ohm's law it can be written P = I²·R or P = V² ÷ R. A bulb's label, such as 60 W at 230 V, tells you the power it takes at that voltage, and so fixes its resistance, R = V² ÷ P = 882 Ω. On another voltage or in another circuit it takes a different power: half the voltage gives a quarter of the power, and two bulbs in series share the voltage, each taking far less than its label. In series the same current flows through both, so the one with more resistance, the lower-rated bulb, takes the larger power: a 60 W bulb outshines a 100 W bulb beside it. Brightness follows the power actually taken, not the number printed on the glass.
A focused learning model
Bulbs keep the resistance their rating gives (a real filament's resistance rises as it heats, so a cold bulb draws more), and the wires and meters are ideal. The supply ramps steadily from 0 over 2 s and holds for 1 s. Brightness follows each bulb's power on a stated scale: full glow at 100 W. The electron dots move at a speed in step with the current, not at the real drift speed. Answers within 2% are right.