HARD
12th Karnataka Board
IMPORTANT
Earn 100

Find current, phase difference, potential and average power used in a pure inductive AC circuit. Also draw phasor diagram.

Important Questions on Alternating Current

MEDIUM
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 22
An inductor has inductance 1 H (i) At what frequency its reactance will be 3140 Ω ? (ii) What will be the capacity of a capacitor to have same reactance at same frequency? 
MEDIUM
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 23
At resonance what is the value of power factor in the case of LCR series circuit? 
HARD
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 24
A bulb of resistance 10 ohm, connected to an inductor of inductance L, is in series with an ac source marked 100V, 50Hz. If the phase angle between the voltage and angle is π4  radian, calculate the value of L.
HARD
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 25
The emf and current of an a.c circuit containing L,C and R are given by ε=ε0sinwt and I=I0sinwt+ϕ. Show that the average power of the circuit is Pavg=εvIvcosϕ, where εv and Iv stand for virtual emf and virtual current respectively.
MEDIUM
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 26

A small town with a demand of 800 kW of electric power at 220 V is situated 15 km away from an electric plant generating power 440 V. The resistance of the two wire line carrying power is 0.5 Ω per km. The town gets power from the line through a 4000-220 V step down transformer at a substation in the town. (a) Estimate the power loss in the form of heat. (b) How much power must the plant supply, assuming there is negligible power loss due to leakage? (c) Characterise the step -up transformer at the plant.

MEDIUM
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 27
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 Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 28
Write down the principle of a transformer and its uses.
HARD
12th Karnataka Board
IMPORTANT
Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 7 - Alternating Current>Exercise>Q 29
A transformer having 5000 turns in its primary steps down 2000 V to 220 V. If the efficiency of the transfer is 80% and output power is 8 kW, find (i) Ns (ii) Ip (iii) Is (iv) Input power where the symbols have their usual meaning.