Question

Circuit Element	ΔV (V)	I (A)	R (Ω)
Battery (Voltage Source)	9	0.24	37.5
R1	2.43	0.24	10
R2	2.92	0.24	12
R3	3.65	0.24	15

a. What is the relationship among the potential drops across each resistor when the resistors are in series? Compare to the potential rise of the power supply.

b. What is the relationship for the current through each resistor when the resistors are in series? Compare with the current through the power supply

c. Compare the total resistance experienced by the potential difference and current through the battery (i.e. the net resistance) to that for the three resistors when combined according to the rules in your textbook/lecture notes.

d. If a fourth resistor were added in series with the other three, what would happen to the total voltage, current, and power delivered by the power supply? What would happen to the potential drops across and currents through the other resistors?

Answer 1

a. When the resistors are connected in series, the voltage of the battery is shared between the resistors based on the ratio of their resistance values. If E is the potential difference applied by battery and V1,V2,V3 are the voltage across resistors then

E = V1+ V2 + V3.

The one with greater resistance will have greater voltage across it.

b) In series connection of resistors, current through each resistor is same as the current drawn from the battery.

Total resistance across battery , R = R1 + R2 + R3 = 37 ohms. But measured value is 37.5 ohms.

Current = V/R = 9/37 = 0.24 A . This one is matching with the measured value.

c) When a fourth resistor is added, Total voltage remains the same, current decreases, power decreases.

The potential drop across each resistor also decreases since the current through the circuit is decreased.