Page 10 - 10-phy-14 Current Electricity
P. 10
Materials Wire wound standard resistors of 22Ω, 27 Ω, and 33 Ω each of 5 watt rating, voltmeter
Required (3V, 15V), ammeter (0.6A,3A), variable power supply (0-12V/1A), connecting wires, 4
one way keys and rheostat (0 – 50 Ω).
Procedure 1. Assemble the circuit as shown in Fig. 14.3.1. Keep all the keys open.
2.
3. Set the rheostat at the middle.
4. Turn the power supply ON. Adjust it to about 6 volts output and close the
key K.
To determine the value of R1, close the key K1. Adjust the rheostat such
that the reading of ammeter is accurately readable. Note the values of V
DO YOU KNOW? and I1 in table 14.3.1. Determine the value of R1 using the relation
R1 = V and record this value in Table 14.3.2.
I¢
Resistors in parallel have
effective resistance which 5. Open key K1 and close key K2. Adjust the rheostat again to bring the
is smaller than that of the 6.
smallest resistor in the voltmeter reading to the same value V. Repeat step 4 to note the current I2
circuit.
and determine the value of R2.
Similarly open key K2 and close key K3 to find the values of I3 and R3.
7. Now close all the keys. Adjust the rheostat to obtain the same value of V as
in steps 4 to 6. Note the values of V and I′.
8. Take two more sets of readings of V and I (step 7) by changing the voltage
V each time with the adjustment of rheostat.
No. Voltmeter Ammeter readings Sum of the currents Difference
of reading through
Obs. (A)
V R1 R2 R3 Re I =I1+I2+I3 I-I¢
1 (V) (A)
Observations I1 I2 I3 I¢ (A)
and Data (A) (A) (A) (A)
Processing
2
3
Table 14.3.1
39
Required (3V, 15V), ammeter (0.6A,3A), variable power supply (0-12V/1A), connecting wires, 4
one way keys and rheostat (0 – 50 Ω).
Procedure 1. Assemble the circuit as shown in Fig. 14.3.1. Keep all the keys open.
2.
3. Set the rheostat at the middle.
4. Turn the power supply ON. Adjust it to about 6 volts output and close the
key K.
To determine the value of R1, close the key K1. Adjust the rheostat such
that the reading of ammeter is accurately readable. Note the values of V
DO YOU KNOW? and I1 in table 14.3.1. Determine the value of R1 using the relation
R1 = V and record this value in Table 14.3.2.
I¢
Resistors in parallel have
effective resistance which 5. Open key K1 and close key K2. Adjust the rheostat again to bring the
is smaller than that of the 6.
smallest resistor in the voltmeter reading to the same value V. Repeat step 4 to note the current I2
circuit.
and determine the value of R2.
Similarly open key K2 and close key K3 to find the values of I3 and R3.
7. Now close all the keys. Adjust the rheostat to obtain the same value of V as
in steps 4 to 6. Note the values of V and I′.
8. Take two more sets of readings of V and I (step 7) by changing the voltage
V each time with the adjustment of rheostat.
No. Voltmeter Ammeter readings Sum of the currents Difference
of reading through
Obs. (A)
V R1 R2 R3 Re I =I1+I2+I3 I-I¢
1 (V) (A)
Observations I1 I2 I3 I¢ (A)
and Data (A) (A) (A) (A)
Processing
2
3
Table 14.3.1
39
