Physics Circuit and Circuit Elements

Ten identical resistances, each of resistance 1 Ω, are joined in parallel. What is the resistance of the combination?

0.1 Ω

Four resistors 2.1Ω, 3.2 Ω, 4.3 Ω, and 5.4 Ω are connected in a series to a 9 V battery. The effective resistance in the circuit is:

15.0 Ω

A filament lamp of resistance 3 Ω is connected to the terminals of a 6 V battery. When the switch is closed, the current in the circuit is:

2 A

Three resistors, 12 Ω, 18 Ω and 36 Ω, are connected in parallel. What is the equivalent resistance?

1 / Req = 1 / R1 + 1 / R2 + 1 / R3 1 / Req = 0.17 Req = 6 Ω

Two light bulbs, each of resistance 3 Ω, are connected in series to a 9 V battery. The current in the circuit is:

1.5 A

Several light bulbs, each of resistance 1.5 Ω, are connected in a series across a 120 V source of emf. If the current through the circuit is 2 A, how many light bulbs are there in the circuit?

Equivalent resistance in the circuit R eq= ∆V/I = 120/2 = 60 Ω Resistance of each bulb = 1.5 Ω No. of bulbs = 60/1.5 = 40

Three resistors, each of resistance 6 Ω, are connected in such a way that that they form the three sides of a triangle. What is the equivalent resistance between any two vertices of the triangle?

Incorrect Answer: Rs = R + R = 2R Rp = (R1R2) / (R1 + R2) Re = (R1(2R)) / (R1 + 2R) Re = (6)(2)(6) / (6 + (2)(6) Re = 4 Ω

Two resistors in series of resistance 6 Ω and 4 Ω are connected across a 12 V battery. What is the potential difference across 6 Ω resistor?

R eq= R 1+ R2 = 6 + 4 = 10 Ω I = ∆V /R eq = 12/10 = 1.2 A Potential difference across R1 = IR1 = 1.2 x 6 = 7.2 V

Two resistors of resistances 3 Ω and 6 Ω are connected in parallel across a 9 V battery. What is the equivalent resistance and the total current in the circuit?

Req = R1 R2 / R1 + R2 = (3 x 6) / (3 +6) =2 Ω I = ∆V/R = 9/2 = 4.5 A

Let n represent the number of similar resistors in a circuit. Each resistor has a resistance of r. When the resistors are connected in parallel the circuit has a total resistance of R. What would the total resistance of the circuit be if the resistors were instead connected in series?

When connected in parallel 1/R = 1/r + 1/r + 1/r + .... = n/r Therefore r = nR When connected in series Rtotal = r + r + r + .... = nr = n(nR) = n2R