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A battery and a variable resistor are in series with a small fan. A switch is closed, and the fan runs. When the variable resistor is moved slightly to the left, the fan slows down a little. When the variable resistor is moved slightly to the right, the fan speeds up a little. If the variable resistor in the circuit is set all the way to the right, what happens in the circuit?
(1) The fan runs faster.
(2) The voltage decreases.
(3) The current increases.
(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II and III

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Last updated date: 20th Jun 2024
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Answer
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Hint: We know that in physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. On the other hand, potential energy is energy that is stored or conserved in an object or substance. This stored energy is based on the position, arrangement or state of the object or substance. We can think of it as energy that has the 'potential' to do work. Based on this concept we have to solve this question.

Complete step by step answer
At first let us define acceleration as the rate of change of velocity. Usually, acceleration means the speed is changing, but not always. When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing.
On the other hand, it should be known to us that velocity is the rate of change of position with respect to time, whereas acceleration is the rate of change of velocity. Both are vector quantities and so also have a specified direction, but the units of velocity are meters per second while the units of acceleration are meters per second squared.
When the resistor is moving left, the resistance in the circuit increases and due to this current decrease, therefore the fan slows down in speed. The reverse is happening when the resistor moves right i.e. fan runs faster.
When the resistor is moving right, the resistance in the circuit decreases and due to this current increase, therefore fan speed up.
If the variable resistor is set to the right, the fan will run faster.

Hence the correct answer is option A.

Note: We should know that kinetic energy is built up in an object by motion and can be defined as the energy that is needed to either slow it down or speed it up. Studies have also been done using kinetic energy and then converting it to other types of energy, which is then used to power everything from flashlights to radios and more. Energy is transferred from one object to another when a reaction takes place. Energy comes in many forms and can be transferred from one object to another as heat, light, or motion, to name a few.
On the other hand, potential energy becomes useful when it is converted to kinetic energy. Kinetic energy is used to perform work. Work occurs when force is applied to an object. Kinetic energy is useful because it allows work to be done. Potential energy is the energy by virtue of an object's position relative to other objects. Potential energy is often associated with restoring forces such as a spring or the force of gravity. This work is stored in the force field, which is said to be stored as potential energy.