Math Problem Statement
A DC motor operates by driving a current through a loop that is immersed in an external magnetic field. The interaction between the current and the external field creates a torque on the loop that causes it to rotate. A very simplified model of a DC motor is attached.
Show that if the loop is a square of side length l = 5 [cm], the current is 𝐼0 = 600.0 [mA], and the external magnetic field strength is |H ̅ | = 5[kA/m], the maximum torque experienced by the loop is [𝐼0l^2𝑚0μ0𝐻0] [Nm]. Be sure to show a picture of the problem, and provide a numerical result being sure to account for the units. In order for this to act as a motor, what needs to happen to the current as the loop rotates?
Solution
To solve the problem, we need to calculate the maximum torque experienced by a square current loop immersed in a magnetic field. Here's the general approach to solving the problem step by step:
Key variables and parameters:
- Side length of the square loop:
- Current in the loop:
- Magnetic field strength:
- is the permeability of free space:
- is also used in Ampere’s law to link the magnetic field to the magnetic induction .
Formula for the torque on a current loop:
The maximum torque on a square loop is given by the formula: where:
- is the current in the loop,
- is the area of the square loop,
- is the magnetic field induction.
Thus, we can express the torque as:
Step 1: Calculate the magnetic induction
Step 2: Compute the area of the square loop
Step 3: Compute the maximum torque
Now, let's compute the maximum torque using all the values. I will calculate the torque numerically.The maximum torque experienced by the square loop is approximately .
To summarize:
- The maximum torque on the loop is .
What needs to happen for this to act as a motor?
In order for the loop to continuously rotate and act as a motor, the direction of the current in the loop needs to reverse every half-turn. This switching of current is typically accomplished using a commutator in a DC motor. It ensures that the torque always acts in the same direction, sustaining the rotational motion.
Would you like further details on any part of the solution, or more clarification on the motor operation?
Here are 5 related questions:
- How does the area of the loop affect the torque?
- What is the role of the commutator in a DC motor?
- How would the torque change if the loop were rectangular instead of square?
- How does the direction of the magnetic field affect the torque on the loop?
- How is torque related to the efficiency of a motor?
Tip: The magnetic induction depends on both the magnetic field and the permeability , so increasing the magnetic field strength will directly increase the torque.
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Math Problem Analysis
Mathematical Concepts
Electromagnetism
Torque
Current Loops
Magnetic Fields
Formulas
Torque (τ) = I * A * B
Magnetic Field (B) = μ0 * H
Area of square loop (A) = l^2
Theorems
Ampere’s Law
Biot-Savart Law
Suitable Grade Level
College-Level Physics
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