Giselle and Anna decided to impress their physical science professor with a simp

Question

Giselle and Anna decided to impress their physical science professor with a simple experiment investigating the resistance of a 100 W lighbulb. They used a VARIAC (which provides a variable voltage to a circuit) in a series circuit with one 100-W lightbulb. They measured the current and voltage, which are listed in the following table. Voltage (Volts) Currents (amps) 120 0.81 100 0.72 80 0.62 60 0.51 40 0.40 20 0.23 Does the resistance of the lighbulb increase or decrease for each voltage and current setting?

Explanation / Answer

Apply V = IR for each set of data

R = V/I

R = 120/.81 = 148

R = 100/.72 = 139

R = 80/.62 = 129

R = 60/.51 = 118

R = 40/.4 = 100

R = 20/.23 = 87

The resistance is decreasing.

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