- A. General Materials & Mathematics
- B. Statics
- C. Kinematics & Dynamics
- D. Rotational Mechanics
- E. Gravitation & Astronomy
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- P. Modern Physics
K5-44. Non-Ohmic Device - Light Bulb
To show the change in resistance of a light bulb with temperature.
Mounted light bulb with double-pole double-throw switch and digital meter.
A 60 watt light bulb is connected to a switch so that it can be quickly disconnected from the 110 VAC◙power to an ohmmeter. The resistance of the 60 watt bulb in operation at a high temperature is R = V^2/P = 110^2/60 = 200 ohms. The resistance cold is about 18 ohms. Turn the bulb on, then switch it to the ohmmeter. The resistance starts high and drops quickly as the bulb cools.