Advertisements
Advertisements
Question
In the circuit shown in fig. 6, find the reading of the ammeter A when the switch S is
(a) Opened.
(b) Closed.
Advertisements
Solution
(a) When the switch S is opened, resistance 60Ω is not connected in the circuit and current flows through the 20Ω resistor.
:. Resistance of the circuit. when the switch is open:
R= 20 + 5 = 25 Ω
Given, voltage = 10 V
:. current through the circuit, I= `"V"/"R" = 10/25` = 0.4 A
The reading of the ammeter is thus 0 .4 A, when the switch is open.
(b) When the switch is closed, resistance 60 Ω gets connected to the circuit.
Thus, in the circuit the parallel combination of 60 Ω and 200 resistors is connected in series with the 5 Ω resistor.
:. Resistance in parallel, `1/"R"_"P" = 1/60 + 1/20 = (1 + 3)/60 = 4/60` Ω
or `"R"_"P" = 15 Ω
Now, total resistance of the circuit= 15 + 5 = 20 Ω
current through the circuit, I= `"V"/"R" = 10/20 = 0.5 "A"`
The reading of the ammeter is thus 0 .5 A, when the switch is closed.
APPEARS IN
RELATED QUESTIONS
By what name is the physical quantity coulomb/second called?
A current of 4 A flows around a circuit for 10 s. How much charge flows past a point in the circuit in this time?
In the circuit diagram given below, three resistors R1, R2, and R3 of 5 Ω, 10 Ω and 30 Ω, respectively are connected as shown
Calculate:
- current through each resistor.
- total current in the circuit.
- total resistance in the circuit.
A battery and three lamps are connected as shown:
Which of the following statements about the currents at X, Y and Z is correct?
(a) The current at Z is greater than that at Y.
(b) The current at Y is greater than that at Z.
(c) The current at X equals the current at Y.
(d) The current at X equals the current at Z.
V1, V2 and V3 are the p.ds. across the 1Ω, 2Ω and 3Ω resistors in the following diagram, and the current is 5 A.
Which one of the columns (a) to (d) shows the correct values of V1, V2 and V3measured in volts?
`V_1` `V_2` `V_3`
(a) 1.0 2.0 3.0
(b) 5.0 10.0 15.0
(c) 5.0 2.5 1.6
(d) 4.0 4.0 2.0
The lamps in a house hold circuit are connected in parallel because:
(a) this way they required less current
(b) if one lamp fails the others remain lit
(c) this way they require less power
(d) if one lamp fails the other also fail
A given wire of resistance 1 Ω is stretched to double its length. What will be its new resistance?
A wire of uniform thickness with a resistance of 27Ω is cut into three equal pieces and they are joined in parallel. Find the equivalent resistance of the parallel combination.
