Skip to main content

Learning Introductory Physics with Activities

Section 28.7 Practice - Faraday’s Law

A*R*C*S 28.7.1. Magnetic Flux.

What is the magnetic flux through an equilateral triangle with side \(60 \mathrm{~cm},\) long, whose plane makes a 60 degree angle with a uniform magnetic field of \(0.33 \mathrm{~T}\text{?}\)

Explanation 28.7.2. The Moving Wire Loop.

The square wire loop below is located below a long straight wire carrying current \(I_w\text{.}\) Each side of the circuit has length \(l\text{.}\)
Figure 28.7.1. A square wire loop moving upward toward a wire.
Make a magnetic induction table for each of the following cases:
  1. The loop is moving upward with constant speed \(v\text{.}\) Choose an area vector into the page.
  2. Repeat case A, but choose the area vector to be in the opposite direction.
  3. Repeat case A, but now the loop is moving downward with constant speed \(v\text{.}\)
  4. Repeat case A, but now the loop is moving to the left with constant speed \(v\text{.}\)
  5. Repeat case A, but now the loop is stationary and the long straight wire is moving upward with constant speed \(v\text{.}\)
Table 28.7.2. Blank Magnetic Induction Table
Quantity Case A Case B Case C Case D Case E
\(\vec{A}\)
\(\vec{B}\)
\(\Phi_B\)
\(\frac{d\Phi_B}{dt}\)
\(V_{ind}\)
\(I_{ind}\)
\(\vec{\mu}_{ind}\)

Subsubsection A*R*C*S Practice

A*R*C*S 28.7.3. Square Loop in a Magnetic Field.

A square loop of wire with side length 6 cm and resistance 0.4 \(\Omega\) is in a uniform magnetic field \(B = -0.008t^2\) (in Tesla) that points in the \(z\)-direction (through the loop). Determine the current induced in the loop as a function of time (both magnitude and direction).

Subsubsection Numerical Practice

Calculation 28.7.4. Induced Current.

A single conducting loop of wire has an area of \(7.40 \times 10^{-2} \ \mathrm{m}^2\) and a resistance of 110 \(\Omega\text{.}\) Perpendicular to the plane of the loop is a magnetic field of strength 0.280 T. At what rate (in T/s) must this field change if the induced current in the loop is to be 0.32 A?
Answer.
476 T/s
Figure 28.7.3. Circular conductive loop in a uniform magnetic field.

Calculation 28.7.5. Conductive Loop in a Magnetic Field.

A conductive metal loop is at rest within a uniform magnetic field, as shown above. If the magnetic field strength is then decreased, in which direction does induced current flow in the loop?
Answer.
There is no current.
Figure 28.7.4. Circular conductive loop falling away from a current carrying wire.

Calculation 28.7.6. Falling Loop.

The figure shows a circular conductive loop falling away from a long wire that is carrying current to the right, as shown above. What is the direction of the induced current in the loop?
Answer.
Clockwise.

References References

[1]
Practice activities provided by BoxSand: https://boxsand.physics.oregonstate.edu/welcome.