For the bridge shown Z1 = 200 ∠20° Ω, Z2 = 150 ∠30° Ω and Z3 = 300 ∠-30° Ω. What is the value of Z4 so that the bridge is balanced?
At bridge balance condition,
Z1 Z4 = Z2 Z3
⇒ 200 ∠20° Z4 = 150 ∠30° 300 ∠-30°
⇒ Z4 = 225 ∠-20° Ω
A simple slide wire potentiometer is used for measurement of current in the circuit. The voltage drop across a standard resistor of 0.6Ω is balanced at 60 cm. The magnitude of current if the standard cell of 4V is balanced at 50 cm is ______ (in A)
Standard cell of 4 V is balanced at 50 cm.
The voltage drop across 60 cm
The working current through the circuit is,
In the bridge circuit shown in figure when then the voltmeter reads
At bridge balance condition
(2R) (Xc) = (2R) (R)
at this condition, bridge is balanced
Hence the voltmeter reading is 0 V.
A resistance potentiometer has a total resistance of 4 kΩ and is rated 10W. If the range of potentiometer is 0 to 200 mm. then its sensitivity is _______ (in V/mm)
R = 4 kΩ
P = 10 W
We know that.
The potentiometer range is 0 to 200 mm.
A length of cable was tested for insulation resistance using loss of charge method. A capacitance formed by sheath of cable of 300 PF is found to have drop in voltage from 300 V to 100 V in 120 seconds. Calculate the insulation resistance of the cable in MΩ
Given that = C = 300 pF
V1 = 300 V
V2 = 100 V
t = 120 S
Calculate the value of effective resistance (in Ω) at a supply frequency of 100 Hz. (C4 = 2 μF)
Under balance condition
Separate and equating real and imaginary part.
Find the excitation frequency (in Hz) in the Ac Bridge shown in figure under balance condition. The circuit component values are given as
R1 = 100 kΩ,
R3 = R4 = 100 kΩ,
C1 = 2 C2 = 10 nF
under bridge balance condition,
Given that, R3 = R4
(1 + jωR1C1)(1 + jωR2C2) = jωC1R2
1 + jωR1C1 + jωR2C2 − ω2R1R2C1C2 = jωC1R2
By comparing real parts on both sides,
By comparing imaginary parts on both sides,
The Schering bridge shown in figure has the following constant R1 = 1.5 kΩ, C1 = 0.4 μF, R2 = 3 kΩ and C3 = 0.4 μF at frequency 1 kHz. The dissipation factor is_______
Given, R1 = 1.5 kΩ
C1 = 0.4 μF
R2 = 3 kΩ
C3 = 0.4 μF
f = 1 kHz
We know that,
and the unknown capacitance
= 2π × 1 × 103 × 0.2 × 10-6 × 3 × 103
The AC bridge is supplied with a source of frequency 5 kHz as shown in the figure. If the bridge is balanced at R1 = 4 R2 and C3 = 20 μF, the value of unknown capacitor Cx is _____ (in μF)
At bridge balanced condition,
By comparing imaginary part,
The dc potentiometer shown in the figure has working current of 10 mA with switch S open. Let Rg + R1 = 100Ω. The galvanometer G can only detect currents greater than 10 μA. The maximum percentage error in the measurement of the unknown e.m.f. Ex as calculated from the slider position shown is closest to
Given that, when the switch is open.
IW = 10 mA
⇒ Rx = 50 Ω.
Length of Rx = 5m.
Resistance across 3m = 30 Ω
Resistance across 2m = 20 Ω
Voltage across 20 Ω = 20 × 10 × 10-3 = 0.2 V
Errors in the reading are due to Rg and R1.
Error = voltage drop across Rg and R1
= Ig (Rg + R1)
= 10 × 10-6 (100) = 1 mV