Efficiency and power loss concepts in Power Electronics - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to define efficiency in power electronics.

Power Electronics

Efficiency (\u03B7) is the ratio of output power to [1] power.

Drag options to blanks, or click blank then click option'

Alost

Binput

Cwasted

Dgenerated

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing input power with lost power.

Thinking efficiency is output power divided by lost power.

Efficiency is calculated as output power divided by input power, showing how well a device converts input energy to useful output.

2fill in blank

medium

Complete the formula to calculate power loss in a device.

Power Electronics

Power loss = [1] power - output power

Drag options to blanks, or click blank then click option'

Ainput

Bwasted

Coutput

Dgenerated

Attempts:

3 left

💡 Hint

Common Mistakes

Using output power instead of input power in the formula.

Confusing power loss with output power.

Power loss is the difference between the input power supplied and the useful output power delivered.

3fill in blank

hard

Fix the error in the efficiency formula below by filling the blank.

Power Electronics

\u03B7 = (output power) / [1] power \u00D7 100%

Drag options to blanks, or click blank then click option'

Ainput

Blost

Cwasted

Dgenerated

Attempts:

3 left

💡 Hint

Common Mistakes

Using lost power instead of input power in the denominator.

Forgetting to multiply by 100% for percentage.

The efficiency formula divides output power by input power, then multiplies by 100 to get a percentage.

4fill in blank

hard

Fill both blanks to complete the expression for power loss percentage.

Power Electronics

Power loss percentage = ([1] power / [2] power) \u00D7 100%

Drag options to blanks, or click blank then click option'

Apower loss

Binput

Coutput

Dwasted

Attempts:

3 left

💡 Hint

Common Mistakes

Using output power instead of input power in the denominator.

Confusing power loss with wasted power.

Power loss percentage is the ratio of power lost to input power, multiplied by 100 to express as a percentage.

5fill in blank

hard

Fill all three blanks to complete the dictionary comprehension for calculating efficiency of devices.

Power Electronics

efficiency = { [1]: ([2] / [3]) * 100 for [1], ([2], [3]) in devices.items() }

Drag options to blanks, or click blank then click option'

Adevice

Boutput_power

Cinput_power

Dpower_loss

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping input and output power variables.

Using power loss instead of output power in the formula.

This comprehension calculates efficiency for each device by dividing output power by input power and multiplying by 100.

Practice

1. What does efficiency in power electronics primarily measure?

easy

A. The voltage drop across components

B. The total power lost as heat

C. The amount of power consumed by the device

D. The ratio of useful power output to total power input

Solution

1. Step 1: Understand efficiency definition

   Efficiency is how well a device converts input power into useful output power.

2. Step 2: Identify correct ratio

   It is the ratio of useful power output to total power input, showing how much input is effectively used.

3. Final Answer:

   The ratio of useful power output to total power input -> Option D

4. Quick Check:

   Efficiency = Useful output / Input power [OK]

Hint: Efficiency = useful output divided by input power [OK]

Common Mistakes:

• Confusing efficiency with power loss
• Thinking efficiency measures total power consumed
• Mixing voltage drop with efficiency

2. Which of the following correctly represents power loss in a power electronic device?

easy

A. Power loss = Output power x Efficiency

B. Power loss = Input power + Output power

C. Power loss = Input power - Output power

D. Power loss = Output power / Input power

Solution

1. Step 1: Recall power loss definition

   Power loss is the energy wasted, usually as heat, which is the difference between input and output power.

2. Step 2: Calculate power loss

   Subtract output power from input power to find the lost power.

3. Final Answer:

   Power loss = Input power - Output power -> Option C

4. Quick Check:

   Power loss = Input - Output [OK]

Hint: Power loss equals input minus output power [OK]

Common Mistakes:

• Multiplying output power by efficiency
• Adding input and output power
• Dividing output by input power

3. Consider a power converter with an input power of 100 W and an efficiency of 90%. What is the power loss in the device?

medium

A. 10 W

B. 90 W

C. 100 W

D. 110 W

Solution

1. Step 1: Calculate output power using efficiency

   Output power = Efficiency x Input power = 0.9 x 100 W = 90 W.

2. Step 2: Find power loss by subtracting output from input

   Power loss = Input power - Output power = 100 W - 90 W = 10 W.

3. Final Answer:

   10 W -> Option A

4. Quick Check:

   Power loss = 100 - 90 = 10 W [OK]

Hint: Power loss = input x (1 - efficiency) [OK]

Common Mistakes:

• Using output power as power loss
• Confusing efficiency percentage with decimal
• Adding input and output power

4. A power device shows an input power of 150 W and output power of 120 W. A student calculates efficiency as 0.75 and power loss as 30 W. What is the error in the calculation?

medium

A. Efficiency should be 0.8, not 0.75

B. Power loss should be 20 W, not 30 W

C. Input power is incorrectly measured

D. Output power should be 150 W

Solution

1. Step 1: Calculate correct efficiency

   Efficiency = Output power / Input power = 120 W / 150 W = 0.8. The student incorrectly calculated it as 0.75.

2. Step 2: Verify power loss calculation

   Power loss = Input - Output = 150 W - 120 W = 30 W, which matches student's value.

3. Step 3: Re-examine efficiency

   The error is in the efficiency, which should be 0.8, not 0.75.

4. Final Answer:

   Efficiency should be 0.8, not 0.75 -> Option A

5. Quick Check:

   Efficiency = 120/150 = 0.8 [OK]

Hint: Efficiency = output/input; check division carefully [OK]

Common Mistakes:

• Mixing up input and output power
• Incorrect division for efficiency
• Assuming power loss is output power

5. A power supply has an efficiency of 85%. If the power loss is reduced by 5 W, what is the new efficiency if the input power remains 200 W?

hard

A. 90%

B. 87.5%

C. 80%

D. 95%

Solution

1. Step 1: Calculate original power loss and output power

   Original power loss = Input power x (1 - Efficiency) = 200 W x (1 - 0.85) = 30 W. Output power = Input - Loss = 200 W - 30 W = 170 W.

2. Step 2: Calculate new power loss and new efficiency

   New power loss = 30 W - 5 W = 25 W. New output power = 200 W - 25 W = 175 W. New efficiency = Output / Input = 175 / 200 = 0.875 or 87.5%.

3. Final Answer:

   87.5% -> Option B

4. Quick Check:

   New efficiency = 175/200 = 0.875 [OK]

Hint: New efficiency = (input - new loss) / input [OK]

Common Mistakes:

• Not recalculating output power after loss change
• Using old efficiency without update
• Confusing power loss with output power