Question

3. The circuit is as shown below. Assuming that the ammeter and voltmeter are ideal, means they don't affect the current in the circuit, so an ideal voltmeter has a very high resistance while an ideal ammeter has a negligible resistance. Voltmeter www 9.0 v 24 (a) What's the ammeter and voltmeter readings with the switch 's' open (0.15 A and 3.6 V (b) What's the ammeter and voltmeter readings with the switch 's' closed? (0.38 A and 9.0V) (e) Now instead of a switch, a 41 resistor is connected in parallel with the 36 resistor as show below, what would be the new ammeter and voltmeter readings? (0.21 A and 5.0 V) 3623 3410 Voltmeter 9.0 v = 24.

Answer 1

3)

Let V = 9.0 V
R1 = 36 ohms
R2 = 24 ohms

a) when S is opened, Req = R1 + R2

= 36 + 24

= 60 ohms

current through the ammeter, I = V/Req

= 9/60

= 0.15 A

volt meter reading = voltage across R2

= I*R2

= 0.15*24

= 3.6 v

b) when S is clsed, Req = R2

= 24 ohms

ammeter reading, I = V/Req

= 9/24

= 0.375 A

= 0.38 A (when rounded to two significant figures)

voltmeter reading = I*R2

= 0.375*24

= 9.0 V

c) let R3 = 41 ohms

Req = R1*R3/(R1 + R3) + R2

= 36*41/(36 + 41) + 24

= 43.17 ohms

current through ammeter, I = V/Req

= 9/43.17

= 0.208 A

= 0.21 A (when rounded to two significant figures)

voltmeter reading = I*R2

= 0.208*24

= 5.0 V