What Voltage is Necessary?

4. To store x₁ mJ of energy in an x₂ μF capacitor, what voltage is necessary?
x₁ and x₂ are some numbers.

Solution:
U = x₁ mJ = x₁ ∙ 10⁻³J
C = x₂ μF = x₂∙ 10⁻⁶ F
V²= 2U/C = 2x₁ ∙ 10⁻³J/(x₂∙ 10⁻⁶ F) = 2∙ 10³x₁/x₂ J/F
V=(2∙10³ x₁/x₂)⁰·⁵ V = 44.7(x₁/x₂)⁰∙⁵ V

Exam 2 Problem 7 Solution

Exam 2 Problem 6 Solution

6. The difference between the highest and lowest voltage of a household "120 V-emf" is ___


Data 
Vrms = 120 V
vmax – vmin =?

Physics Formulas
Amplitude V=√2 Vrms
Vmax – Vmin = 2V = 2∙Amplitude 

Solution
Vmax  – Vmin  = 2V = 2∙√2 Vrms
Vmax  – Vmin= 2∙√2∙120V= 339V

Exam 2 Problem 5 Solution

Solutions: Chapter 21, Problems 4, 7

Chapter 21, Problem 4. A single loop of wire with an area of x₁ m² is in a uniform magnetic field that has an initial value of x₂ T, is perpendicular to the plane of the loop, and is decreased with the constant rate of x₃ T/s.
(a) What emf is induced in this loop?

(b) If the loop has a resistance of x₄ Ω, find the current induced in the loop.

Chapter 21, problem 7. A closely wound rectangular coil of N turns has dimensions of x₁ cm by x₂ cm. The plane of the coil is rotated from a position where it makes an angle of x₃ᵒ with a magnetic field of x₄ T to a position perpendicular to the field. The rotation takes x₅ s.
What is average emf induced on the coil?

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