EASY
12th CBSE
IMPORTANT
Earn 100

A coil of 0.01 henry inductance and 1 ohm resistance is connected to 200 volt, 50 Hz ac supply. Find the impedance of the circuit and time lag between max. alternating voltage and current.

Important Questions on Alternating Current

MEDIUM
12th CBSE
IMPORTANT
A 60 W load is connected to the secondary of a transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.
MEDIUM
12th CBSE
IMPORTANT
Explain why the reactance provided by a capacitor to an alternating current decreases with increasing frequency.
MEDIUM
12th CBSE
IMPORTANT
Explain why the reactance offered by an inductor increases with the increasing frequency of an alternating voltage.
HARD
12th CBSE
IMPORTANT
An electrical device draws 2 kW, 50 kV power from AC mains voltage 223 V (rms). The current differs (lags) in phase by ϕ tanϕ=-34 as compared to voltage. Find (i) R, (ii) XC-XL, and (iii) IM. Another device has twice the values for R, XC and XL. How are the answers affected?
 
MEDIUM
12th CBSE
IMPORTANT
1 MW power is to be delivered from a power station to a town 10 km away. One uses a pair of Cu wires of radius 0.5 cm for this purpose. Calculate the fraction of ohmic losses to the power transmitted if
(i) power is transmitted at 220V. Comment on the feasibility of doing this.
 
MEDIUM
12th CBSE
IMPORTANT

1 MW power is to be delivered from a power station to a town 10 km away. One uses a pair of Cu wires of radius 0.5 cm for this purpose. Calculate the fraction of ohmic losses to the power transmitted if
(ii) a step-up transformer is used to boost the voltage to 11000 V, power transmitted, then a step-down transformer is used to bring the voltage to 220 V.

MEDIUM
12th CBSE
IMPORTANT

Consider the LCR circuit shown in Fig 7.6. Find the net current i and the phase of i. Show that i=vZ.
Find the impedence Z for this circuit.

Question Image

 

HARD
12th CBSE
IMPORTANT

For an LCR circuit driven at frequency ω, the equation reads

Ldidt+Ri+qC=vt=vm sin ωt

Multiply the equation by i and simplify where possible.