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A rectangular coil \(25 \mathrm{cm}\) by \(35 \mathrm{cm}\) has 120 turns. This coil produces a maximum emf of \(65 \mathrm{V}\) when it rotates with an angular speed of \(190 \mathrm{rad} / \mathrm{s}\) in a magnetic field of strength \(B .\) Find the value of \(B.\)

Short Answer

Expert verified
The magnetic field strength is approximately 0.0326 T.

Step by step solution

01

Understand the formula for maximum emf

The maximum emf (\( \varepsilon_{max} \)) produced by a rotating coil in a magnetic field is given by the formula: \[\varepsilon_{max} = NAB\omega\sin\theta\]where:- \(N = 120\) is the number of turns,- \(A\) is the area of the coil,- \(B\) is the magnetic field strength,- \(\omega = 190 \, \mathrm{rad/s}\) is the angular speed - \(\sin \theta = 1\) because the emf is maximum when the plane of the coil is perpendicular to the magnetic field (\(\theta = 90^\circ\)).Rearrange the formula to solve for \(B\):\[ B = \frac{\varepsilon_{max}}{NA\omega} \]
02

Calculate the area of the coil

The area \(A\) of the rectangular coil is given by the product of its length and width:\[ A = 0.25 \, \mathrm{m} \times 0.35 \, \mathrm{m} \]\[ A = 0.0875 \, \mathrm{m^2} \]
03

Substitute the values into the rearranged formula

Substitute \(\varepsilon_{max} = 65 \, \mathrm{V}\), \(N = 120\), \(A = 0.0875 \, \mathrm{m^2}\), and \(\omega = 190 \, \mathrm{rad/s}\) into the equation for \(B\):\[ B = \frac{65}{120 \times 0.0875 \times 190} \]
04

Calculate the magnetic field strength

Calculate \(B\) using the substituted values:\[ B = \frac{65}{1995} \approx 0.0326 \, \mathrm{T} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Rectangular Coil
A rectangular coil is a loop of wire shaped into a rectangle. In our exercise, the coil is specifically 25 cm by 35 cm. Converting these to meters, it becomes 0.25 m by 0.35 m. The coil in the problem has 120 turns, meaning it consists of 120 loops of wire stacked or wound closely together. The purpose of a coil is to efficiently induce electromotive force, or emf, which is an electrical potential produced by a changing magnetic environment. The size and dimensions of the coil influence the amount of emf generated because they determine the coil's area. A larger area generally results in more emf when all other factors remain constant. The construction and geometry of the coil enable it to maximize interaction with the magnetic field, enhancing its ability to produce current when rotating.
Maximum EMF
Maximum emf is the peak electrical potential generated by the coil under optimal conditions. This occurs when the coil's rotation brings it to be perpendicular to the magnetic field, maximizing the change in magnetic flux. In the formula, \[\varepsilon_{max} = NAB\omega\sin\theta\]we see how maximum emf depends on several factors:- \(N\): the number of turns in the coil, which intensifies the emf- \(A\): the area of the coil, which relates to how much magnetic field the coil can intercept- \(B\): the magnetic field strength- \(\omega\): the angular velocity, indicating how fast the coil turnsThe term \(\sin\theta\) accounts for the angle, and in maximum emf cases, \(\theta\) is 90 degrees, making \(\sin 90^\circ = 1\). This simplifies calculations when optimizing the emf output.
Angular Speed
Angular speed describes how quickly the coil rotates. It is given in radians per second (rad/s). In the exercise, the coil rotates with an angular speed of 190 rad/s, which is quite rapid, ensuring frequent changes in the magnetic flux. Angular speed is critical because it directly influences how often and intensely the magnetic field interacts with the coil. A faster rotation means greater change in magnetic flux per unit time, enhancing the emf produced by Faraday's law of electromagnetic induction. The faster the angular speed, the more potential there is for the coil to reach its maximum emf value, due to the rapid rate at which it sweeps through the magnetic field lines.
Magnetic Field Strength
Magnetic field strength, represented as \(B\), is a measure of the magnetic influence. It is measured in teslas (T) and determines how strongly the magnetic field can induce current in the coil. In the context of our problem, we calculated \(B\) to be approximately 0.0326 T. This value provides insight into how much magnetic force the coil is exposed to.The magnetic field strength combines with the coil's characteristics to influence the maximum emf. The power of \(B\) lies in its ability to facilitate the conversion of kinetic (rotational) energy from the turning coil into electrical energy.A stronger magnetic field results in a greater emf for a given coil and rotational speed, thus highlighting the importance of \(B\) in electromagnetic induction processes.

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