Johdinsilmukan halkaisija on 1.9 cm, ja se on homogeenisessa magneettikentässä siten, että kenttäviivojen ja silmukan normaalin välinen kulma on 62 astetta. Magneettikentän muuttuessa silmukkaan indusoituu itseisarvoltaan 4.1 mV:n jännite. Kuinka suuri tällöin on magneettikentän muutosnopeuden itseisarvo? Anna vastaus yksiköissä T/s yhden desimaalin tarkkuudella.A wire loop with diameter of 1.9 cm is in a uniform magnetic field such that the angle between field lines and the the normal of the loop is 62 degrees. The change of the magnetic field induces in the loop the voltage with the absolute value of 4.1 mV. How great is then the rate of change of the absolute value of the magnetic field? Give your answer in units T/s with one decimal accuracy.

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Question restatement: A wire loop with diameter 1.9 cm sits in a uniform magnetic field. The angle between the magnetic field lines and the loop’s normal is 62 degrees. As the magnetic field changes, the loop experiences an induced emf (voltage) with absolute value 4.1 mV. Determine the absolute value of the rate of change of the magnetic field, d|B|/dt, in teslas per second (T/s) to one decimal place.

First, compute the loop area. The radius is half the diameter: r = 1.9 cm / 2 = 0.95 cm = 0.0095 m. The area is A = πr^2 = π(0.0095 m)^2 ≈ 3.1416 × 9.025×10^-5 m^2 ≈ 2.836×10^-4 m^2.

Next, recall the magnetic flux through the loop: Φ = B · A · cos(φ), where φ is the angle between B and the loop’s normal. The problem states φ = 62°. Since φ is constant while B changes, the time derivative of the flux is dΦ/dt = A cos(φ) dB/dt. The induced emf magnitude is ε = |dΦ/dt| = A cos(φ) |dB/dt|.

Convert the given emf to volts: ε = 4.1 mV = 4.1×10^-3 V. Compute cos(φ): cos(62°) ≈ 0.4695. Then A cos(φ) ≈ (2.836×10^-4 m^2) × 0.4695 ≈ 1.331×10^-4 m^2.

Solve for the rate of change of the magnetic field: |dB/dt| = ε / (A cos(φ)) ≈ (4.1×10^-3 V) / (1.331×10^-4 m^2) ≈ 30.8 T/s.

Rounding to one decimal place as requested, the magnitude of the rate of change of the magnetic field is about 30.8 T/s.

Note on options: The provided data includes the numeric answer 30.8, but no separate multiple-choice options were given to analyze. The result above follows directly from the standard emf-flux relation and the geometry given in the problem.

Dashboard QUIZ Exercise 5

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