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Q. 64

Physics for Scientists and Engineers: A Strategic Approach with Modern Physics
Found in: Page 793

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Short Answer

For what emf does the resistor in dissipate no power? Should the emf be oriented with its positive terminal at the top or at the bottom?

and the positive terminal is bottom

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Step by Step Solution

Step 1 : Given Information

We should find oriented with its positive terminal at the top or at the bottom.

Step 2 : Simplify

When the current flows through a resistor, it dissipates energy, the rater of the dissipated energy is the power. This rate where the energy is transferred to the current to the resistor is

The dissipated power is zero when the current through the resistor is zero (no current flow). But at the condition, the current will not flow through the ? This occurs when the right battery applies a current through with the same magnitude of the left battery but in opposite direction. So, let us find the current that is flow due the left battery using Ohm's law.

Ohm's law states that the current I flows through a resistance due to the potential difference V between resistance.

So, we get the current through by using the values into equation

As we mentioned above, this is the current that flows in to make no current flows through . So, the voltage that exert this current through the resistor is calculated by Ohm's law in the form

The right battery has emf and to exerts a current in the opposite direction, its terminal positive should be bottom.

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