Question

Experiment: With the battery voltage set to 15 volts, measure the current in a parallel circuit with 1, 2, 3, and 4 light bulbs. (In each case, place the ammeter next to the battery.) Use Ohm’s law to calculate the total resistance of the circuit. Record results below. Is this right?

Answer 1

No

Step-by-step explanation:

We expect current to be proportional to the number of identical bulbs. The total resistance is the ratio of voltage to current, so will be inversely proportional to the number of bulbs.

The current readings look wrong in that the first bulb caused the current to be 1 A, but each additional bulb increased it by 2 A. If that is what happened, the bulbs were not identical. That may be OK, but we expect the point of the experiment is to let you see the result described above.

In any event, the total resistance is not calculated properly. It should be the result of dividing voltage (15 V) by current.

Answer 2

No, it is not right.

Step-by-step explanation:

Your table is not consistent with bulbs of the same resistance.

Current comes from a measurement, but resistance comes from a calculation.

I presume that the measured currents are correct.

Ohm's Law states that the current flowing in a circuit is directly proportional to the voltage.

We usually write it as

V/I = R

1. One bulb in circuit

`R = (V)/(I) = \frac{\text{15 V}}{\text{1 A}}= \mathbf{15 \, \Omega}`

2. Two bulbs

`R = (V)/(I) = \frac{\text{15 V}}{\text{3 A}} = \mathbf{5 \, \Omega}`

3. Three bulbs

`R = (V)/(I) = \frac{\text{15 V}}{\text{5 A}} = \mathbf{3 \, \Omega}`

4. Four bulbs

`R = (V)/(I) = \frac{\text{15 V}}{\text{7 A}} = \mathbf{2.1 \, \Omega}`