Motor torque and speed characteristics in EV Technology - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to describe motor torque: Torque is the {{BLANK_1}} that causes an object to rotate.

EV Technology

Torque is the [1] that causes an object to rotate.

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

Aforce

Bspeed

Cenergy

Dpower

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing torque with speed or power.

Torque is a force that causes rotation around an axis.

2fill in blank

medium

Complete the sentence: Motor speed is usually measured in {{BLANK_1}}.

EV Technology

Motor speed is usually measured in [1].

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

Avolts

Bwatts

Cnewtons

Drevolutions per minute

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing speed units with power or force units.

Motor speed is commonly measured in revolutions per minute (RPM), indicating how many times the motor shaft turns in one minute.

3fill in blank

hard

Fix the error in the statement: Torque decreases as motor {{BLANK_1}} increases.

EV Technology

Torque decreases as motor [1] increases.

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

Apower

Bspeed

Ccurrent

Dvoltage

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing power or voltage instead of speed.

In many motors, torque decreases as speed increases due to the motor's characteristics.

4fill in blank

hard

Fill both blanks to complete the relationship: When motor {{BLANK_1}} increases, the {{BLANK_2}} usually decreases.

EV Technology

When motor [1] increases, the [2] usually decreases.

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

Aspeed

Btorque

Cpower

Dvoltage

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up torque and power.

As motor speed increases, torque typically decreases because the motor produces less turning force at higher speeds.

5fill in blank

hard

Fill all three blanks to complete the dictionary comprehension: motor_data = { {{BLANK_1}}: {{BLANK_2}} for {{BLANK_3}} in measurements if measurements[{{BLANK_3}}] > 0 }

EV Technology

motor_data = { [1]: [2] for [3] in measurements if measurements[[3]] > 0 }

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

Aspeed

Btorque

Cmeasurement

Dpower

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing keys and values or loop variable names.

This comprehension creates a dictionary where keys are measurement names, values are torque values, and it loops over speed measurements greater than zero.

Practice

1. What does torque in an electric motor represent?

easy

A. The twisting force that makes the motor shaft rotate

B. The speed at which the motor shaft spins

C. The electrical power consumed by the motor

D. The temperature of the motor during operation

Solution

1. Step 1: Understand the definition of torque

   Torque is the force that causes rotation around an axis, in this case, the motor shaft.

2. Step 2: Differentiate torque from speed and power

   Speed is how fast the shaft spins, power is the product of torque and speed, so torque specifically means the twisting force.

3. Final Answer:

   The twisting force that makes the motor shaft rotate -> Option A

4. Quick Check:

   Torque = twisting force [OK]

Hint: Torque means twisting force, not speed or power [OK]

Common Mistakes:

• Confusing torque with speed
• Thinking torque is power output
• Mixing torque with electrical current

2. Which of the following correctly describes the relationship between torque and speed in a typical electric motor?

easy

A. Torque and speed are always equal

B. Torque increases as speed increases

C. Torque decreases as speed increases

D. Torque and speed are unrelated

Solution

1. Step 1: Recall the typical torque-speed curve for electric motors

   In many motors, torque is highest at low speed and decreases as speed increases.

2. Step 2: Understand the inverse relationship

   As the motor spins faster, the torque it can provide usually drops, showing an inverse relationship.

3. Final Answer:

   Torque decreases as speed increases -> Option C

4. Quick Check:

   Torque and speed have inverse relation [OK]

Hint: Torque usually drops when speed goes up [OK]

Common Mistakes:

• Assuming torque grows with speed
• Thinking torque equals speed
• Ignoring the motor's torque-speed curve

3. Consider a motor running at 1000 RPM producing 50 Nm torque. If the speed doubles to 2000 RPM and torque halves, what happens to the motor's power output?

medium

A. Power doubles

B. Power stays the same

C. Power halves

D. Power quadruples

Solution

1. Step 1: Calculate initial power

   Power = Torque x Speed. Initial power = 50 Nm x 1000 RPM = 50,000 (units simplified).

2. Step 2: Calculate new power after changes

   New torque = 50 / 2 = 25 Nm, new speed = 1000 x 2 = 2000 RPM. New power = 25 Nm x 2000 RPM = 50,000.

3. Final Answer:

   Power stays the same -> Option B

4. Quick Check:

   Power = Torque x Speed = constant [OK]

Hint: Power = torque x speed; doubling speed and halving torque keeps power same [OK]

Common Mistakes:

• Multiplying changes incorrectly
• Forgetting to halve torque
• Assuming power changes linearly with speed only

4. A motor's torque-speed graph shows torque dropping linearly from 100 Nm at 0 RPM to 0 Nm at 3000 RPM. If the motor is running at 1500 RPM, what is the torque? Identify the error in this calculation: Torque = 100 - (1500 / 3000) x 100 = 50 Nm.

medium

A. The calculation is correct

B. The torque should be 75 Nm, not 50 Nm

C. The torque should be 25 Nm, not 50 Nm

D. The torque cannot be calculated from this graph

Solution

1. Step 1: Understand the linear torque-speed relation

   Torque decreases from 100 Nm at 0 RPM to 0 Nm at 3000 RPM, so torque at any speed is 100 x (1 - speed/3000).

2. Step 2: Calculate torque at 1500 RPM

   Torque = 100 x (1 - 1500/3000) = 100 x 0.5 = 50 Nm, matching the given calculation.

3. Final Answer:

   The calculation is correct -> Option A

4. Quick Check:

   Torque at half speed = half torque [OK]

Hint: Torque halves at half max speed in linear drop [OK]

Common Mistakes:

• Misapplying the formula
• Confusing RPM ratio direction
• Assuming torque is constant

5. An electric vehicle motor has a torque-speed characteristic where torque is constant at 200 Nm up to 2000 RPM, then decreases linearly to 0 Nm at 6000 RPM. What is the torque at 4000 RPM?

hard

A. 50 Nm

B. 150 Nm

C. 200 Nm

D. 100 Nm

Solution

1. Step 1: Identify torque behavior zones

   Torque is constant 200 Nm up to 2000 RPM, then decreases linearly to 0 Nm at 6000 RPM.

2. Step 2: Calculate torque at 4000 RPM

   From 2000 to 6000 RPM (a 4000 RPM range), torque drops from 200 Nm to 0. At 4000 RPM, which is 2000 RPM into this range, torque = 200 x (1 - 2000/4000) = 200 x 0.5 = 100 Nm.

3. Final Answer:

   100 Nm -> Option D

4. Quick Check:

   Halfway in drop range means half torque [OK]

Hint: Calculate linear drop after constant torque zone [OK]

Common Mistakes:

• Using full RPM instead of drop range
• Forgetting constant torque zone
• Mixing RPM values in formula