Introduction:
A single phase induction motor is a type of motor that is widely used in various applications. It is primarily used in small appliances and equipment due to its simple construction and low cost. In order to start a single phase induction motor, a capacitor is used.

Explanation:
The use of a capacitor in a single phase induction motor serves the purpose of starting the motor. Let's understand why it is necessary and how it works.

Starting Mechanism:
A single phase induction motor requires a rotating magnetic field to start. In a three-phase motor, the rotating magnetic field is easily generated by the three-phase power supply. However, in a single phase motor, the power supply is single-phase, which means it cannot generate a rotating magnetic field on its own.

Split Phase Capacitor Start Motor:
To overcome this limitation, a capacitor is connected in series with the auxiliary winding of the single phase induction motor. This configuration is commonly known as a split-phase capacitor start motor. The capacitor introduces a phase shift between the main and auxiliary windings, allowing the motor to generate a rotating magnetic field.

Role of Capacitor:
The capacitor used in the single phase induction motor has two main functions:
1. Phase Shifting: The capacitor introduces a phase shift between the main and auxiliary windings. This phase shift creates a rotating magnetic field, which is essential for motor starting.
2. Starting Torque: The capacitor also helps in improving the starting torque of the motor. By providing the necessary phase shift, the capacitor helps in generating a stronger rotating magnetic field, resulting in higher starting torque.

Conclusion:
In summary, the use of a capacitor in a single phase induction motor is essential for starting the motor. The capacitor introduces a phase shift between the main and auxiliary windings, allowing the motor to generate a rotating magnetic field. This phase shift not only enables motor starting but also improves the starting torque. Therefore, the correct answer is option C - starting the motor.