# Electric Vehicles | Week 3

Course Name: Electric Vehicles – Part 1

#### Q1. Angular velocity of the motor is 900 rad/sec. Find velocity of wheel for a diameter of 0.3 m and gear ratio of 5. Choose the correct option.a. 9 km/hrb. 18 km/hrc. 97.2 km/hrd. 64.8 km/hr

Q2. The average velocity of the vehicle is 180 km/hr. It requires 4000 W for operation of 30 min. Find the magnitude of constant tractive effort.
a. 11 N
b. 30 N
c. 18 N
d. 80 N

These are Electric Vehicles Week 3 Assignment 3 Answers NPTEL

A) In constant tractive effort case, linear acceleration of the vehicle directly depend on the velocity of the vehicle.
B) Gears are used to increase the speed at wheels.
C) In constant tractive effort case, velocity of the vehicle is affected by the air drag coefficient.

a. A)-False, B)-False, C)-False
b. A)-False, B)-False, C)-True
c. A)-True, B)-False, C)-True
d. A)-True, B)-True, C)-False

A) Forward moving direction of vehicle is lateral direction.
B) For very high speed vehicles, understanding of lateral dynamics is more important.
C) When a vehicle moves, a high pressure area is created near its frontal plane due to trapping of air.

a. A)-False, B)-False, C)-False
b. A)-False, B)-True, C)-True
c. A)-True, B)-False, C)-True
d. A)-True, B)-True, C)-False

These are Electric Vehicles Week 3 Assignment 3 Answers NPTEL

Q5. If the speed of the vehicle is 72 km/Hr, find the angular velocity of the motor for a wheel diameter of 0.2 m and gear ratio of 10. Choose the correct option.

A) The motor speed is greater than wheel speed.
B) The output power of the motor is positive during hill climbing.
C) The wheel torque is lower than motor torque.

a. A)-True, B)-False, C)-False
b. A)-True, B)-True, C)-False
c. A)-False, B)-False, C)-True
d. A)-False, B)-True, C)-True

These are Electric Vehicles Week 3 Assignment 3 Answers NPTEL

Q7. If the wheel diameter, gear ratio and speed of the vehicle are all doubled. What will be its effect on the rpm of the electric motor? Choose the correct option.
a. It will become twice
b. It will become half
c. No change
d. It will become four times

Answer: a. It will become twice

A) Aerodynamic coefficient is dependent on streamlining of the vehicle.
B) Air density is a function of temperature.
C) Rolling resistance force decreases with decrease tyre pressure.

a. A)-False, B)-False, C)-False
b. A)-True, B)-False, C)-True
c. A)-True, B)-true, C)-False
d. A)-False, B)-True, C)-True

These are Electric Vehicles Week 3 Assignment 3 Answers NPTEL

A) Aerodynamic drag force is lower in cold climate.
B) Ground Clearance should be decreased for low aerodynamic drag force.
C) Wind Velocity always increases aerodynamic drag force.

a. A)-True, B)-True, C)-False
b. A)-True, B)-False, C)-False
c. A)-False, B)-False, C)-True
d. A)-False, B)-True, C)-False

These are Electric Vehicles Week 3 Assignment 3 Answers NPTEL

A) Gradability is calculated when the vehicle is accelerating.
B) Tractive effort and vehicle speed always have a linear relation.
C) Torque on wheel is proportional to its diameter.

a. A)-False, B)-False, C)-False
b. A)-True, B)-False, C)-True
c. A)-False, B)-False, C)-True
d. A)-True, B)-True, C)-False