If the work done on the system or by the system is zero, then which one of the following statement for a gas kept at a certain temperature is correct?

Consider the following part of an electric circuit.

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The total electrical resistance in the given part of the electric circuit is

Which one of the following statements regarding lenses is not correct?

10 g of ice at $$-$$10$$^\circ$$ C is mixed with 10 g of water at 0$$^\circ$$ C. The amount of heat required to raise the temperature of mixture to 10$$^\circ$$ C is