Case Study:

In cities like Delhi and Bengaluru, electric vehicles (EVs) are becoming increasingly popular due to rising fuel costs and environmental concerns. At a public EV charging station in Delhi, a car with a 40 kWh battery capacity is being charged using a fast charger rated at 20 kW.

The charging process involves converting AC supply into DC to store energy in the battery. The power relation used is:

P = VI

If the charger operates at 400 V, the current drawn is:
I = P / V = 20000 / 400 = 50 A

Ideally, the time required to fully charge the battery is:
Time = Energy / Power = 40 kWh / 20 kW = 2 hours

However, due to inefficiencies such as heat loss, resistance in wires, and battery limitations, the actual efficiency is around 85%. Therefore, the effective charging time increases:

Actual energy required = 40 / 0.85 ≈ 47 kWh
Actual time ≈ 47 / 20 = 2.35 hours

Additionally, during peak hours, voltage fluctuations and grid load can reduce charging speed. Engineers are working on ultra-fast chargers and improved battery technology to reduce charging time and energy losses.

This case highlights how physics concepts like power, current, resistance, and efficiency are crucial in modern transportation systems and sustainable energy solutions in India.

Questions:

Section A - MCQs

1. What is the current drawn by the charger operating at 400 V and 20 kW?

A. 20 A
B. 40 A
C. 50 A
D. 80 A

2. Why does actual charging time exceed ideal time?

A. Higher voltage
B. Energy losses and inefficiency
C. Lower battery capacity
D. Increased current

3. What is the ideal time required to charge a 40 kWh battery with a 20 kW charger?

A. 1 hour
B. 2 hours
C. 3 hours
D. 4 hours

4. What happens during voltage fluctuation at charging stations?

A. Charging speed increases
B. Charging stops completely
C. Charging speed may decrease
D. Battery capacity increases

Section B - Short Answer Questions

1. Calculate the current drawn during charging.

2. Explain one reason for energy loss during EV charging.

3. Why is efficiency important in EV charging systems?

Section C - Long Answer Question

1. If a new fast charger of 40 kW is used with the same efficiency (85%), calculate the new charging time. Analyze how increasing power affects efficiency, cost, and infrastructure requirements.

Answer Key:

Section A - MCQs Answers:

1. C
2. B
3. B
4. C

Section B - Short Answers:

1. I = P / V = 20000 / 400 = 50 A

2. Energy is lost as heat due to resistance in wires and internal battery processes, reducing overall efficiency.

3. Higher efficiency ensures less energy loss, faster charging, and lower electricity costs.

Section C - Long Answer:

• New power = 40 kW
• Required energy = 47 kWh (considering 85% efficiency)

Time = 47 / 40 = 1.175 hours ≈ 1.18 hours

Analysis:

• Charging time reduces significantly
• Requires stronger infrastructure and higher current
• Increased cost of installation
• May generate more heat --> cooling needed
• Improves user convenience and EV adoption