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What amount of heat will be generated in a coil of resistance R due to a charge q passing through it if the current in the coil, 
a decreases down to zero uniformly during a time interval Δt, 
b decreases down to zero halving its value every Δt seconds?

Important Questions on ELECTRODYNAMICS

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JEE Main
IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.190.

A DC source with internal resistance R0 is loaded with three identical resistances R interconnected as shown in the figure. 

At what value of R will the thermal power generated in this circuit be the highest? 

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JEE Main
IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.191.
Make sure that the current distribution over two resistances R1 and R2 connected in parallel corresponds to the minimum thermal power generated in this circuit.
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IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.192.
A storage battery with emf E=2.6 V loaded with an external resistance produces a current I=1.0 A. In this case the potential difference between the terminals of the storage battery equals V=2.0 V. Find the thermal power generated in the battery and the power developed in it by electric forces.
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Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.193.
A voltage V is applied to a dc electric motor. The armature winding resistance is equal to R. At what value of the current flowing through the winding will the useful power of the motor be the highest? What is it equal to? What is the motor efficiency in this case?
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IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.194.
How much (in per cent) has a filament diameter decreased due to evaporation, if the maintenance of the previous temperature required an increase of the voltage by η=1.0%? The amount of heat transferred from the filament into surrounding space is assumed to be proportional to the filament surface area.
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Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.195.
A conductor has a temperature-independent resistance  R and a total heat capacity C. At the moment i=0, it is connected to a DC voltage V. Find the time dependence of a conductor's temperature T assuming the thermal power dissipated into surrounding space to vary as q=kT-T0, where k is a constant, T0 is the environmental temperature (equal to the conductor's temperature at the initial moment).
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IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.196.

A circuit as shown in the figure has resistances R1=20 Ω and R2=30 Ω. At what value of the resistance Rx will the thermal power generated in it be practically independent of small variations of that resistance?

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The voltage between the points A and B is supposed to be constant in this case.

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JEE Main
IMPORTANT
Problems in General Physics>Chapter 3 - ELECTRODYNAMICS>ELECTRIC CURRENT>Q 3.197.

In a circuit shown in the figure, resistances R1 and R2 are known, as well as emf's E1 and E2. The internal resistances of the sources are negligible. At what value of the resistance R, will the thermal power generated in it be the highest? What is it equal to?

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