How much current does the motor draw to produce the required torque?

In summary, a small electric car with ten 12.0V batteries connected in series overcomes a 269N friction force while traveling at 28.6km/hr. The electric motor is coupled directly to the wheels with a diameter of 50.6cm and has 295 armature coils that rotate in a 0.590T magnetic field. To produce the required torque, the motor draws a current which can be calculated using the torque equations. The question of back emf and power dissipation in the coils remains unanswered due to insufficient information.
  • #1
xSnoopy
9
0

Homework Statement


A small electric car overcomes a 269N friction force when traveling 28.6km/hr. The electric motor is powered by ten 12.0V batteries connected in series and is coupled directly to the wheels whose diameters are 50.6cm. The 295 armature coils are rectangular, 10.0cm by 14.8cm, and rotate in a 0.590T magnetic field. How much current does the motor draw to produce the required torque?


What is the back emf?

How much power is dissipated in the coils?


Homework Equations


Not too sure...

The Attempt at a Solution


This is kind of weird as my homework goes from Waves and EM to this question :S regardless...

I'm not really sure where to start on this, I was guessing that the armature coil would be producing a current I? So:

B=μIn, where B=0.590T and n = 295/(0.148m) but I'm guessing that's not it at all...

Any help?
 
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  • #2
Okay I seem to got the first part

Torque on Wheel = Torque on coils in motor

TorqueWheel = ForceFriction*RadiusWheel

TorqueCoil = B*I*(AreaCoil)

Where I can solve for I or current. :)

But now I'm stuck on calculating the back emf...
I guess I know...

V(battery) - IR = emf or -L(dI/dt) = emf but I don't have either R or L... Any help?
 
  • #3
Is it easier than you think? You know the force and velocity so you know the power required. You know the battery voltage so presumably you can calculate the current from P=IV.

Is the rest of the info unnecessary? I don't think there is enough info to calculate the motor efficiency?
 

Related to How much current does the motor draw to produce the required torque?

1. What is the relationship between current and torque in a motor?

The amount of current drawn by a motor is directly proportional to the torque it produces. This means that as the required torque increases, the current drawn by the motor will also increase.

2. How do you measure the current drawn by a motor?

The current drawn by a motor can be measured using a multimeter, which is a device that measures electrical current. The multimeter is connected in series with the motor, and the reading on the multimeter will indicate the amount of current flowing through the motor.

3. What factors affect the amount of current drawn by a motor?

The amount of current drawn by a motor is affected by various factors, including the size and type of motor, the load on the motor, the supply voltage, and the efficiency of the motor. These factors can all impact the amount of torque produced by the motor and therefore influence the current drawn.

4. Can a motor draw too much current?

Yes, a motor can draw too much current, which can lead to overheating and potentially cause damage to the motor. It is important to ensure that the motor is not overloaded and that the current drawn is within the motor's rated capacity.

5. How can you calculate the current drawn by a motor?

The current drawn by a motor can be calculated using Ohm's law, which states that current (I) equals voltage (V) divided by resistance (R). In a motor, the resistance is typically very low, so the current can be approximated by dividing the voltage by the motor's rated power. However, this calculation may not be accurate for all types of motors, and it is best to measure the current directly using a multimeter.

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