Test 3 Variant 4 Group Name (TYPE) NO communications NO phones and any devices 1) A point charge q = -5 μC is surrounded by a 7) Find the power of energy dissipation P in the sphere with radius r = 1 m. resistor R = 100 Ω, if current I = 5 mA. Find the electric flux Ф through the sphere. Coulomb’s constant is k = 9×109 N·m2·C-2 Ans.: 2) Find the equivalent capacitance, when the three capacitors С1 = 8 nF, С2 = 20 nF, and С3 = 40 nF are connected in series. Ans.: 8) The proton (q = +1.6×10-19 C) has velocity υ = 2105 m/s. The uniform magnetic field with magnitude B = 5 T has angle with velocity direction α = 180°. Find Lorentz force F. Ans.: 3) Find the electric potential energy U for a charge q = +4 mC at the distance r = 9 cm from charge Q = +40 C. Ans.: 9) Two straight, parallel, superconducting cables 4.5 mm apart carry equal currents of I = 1.5×10-3 kA. Length of cables is l = 1 m. Find force F of interaction between these cables. μ0 = 4π×10-7 TmA-1 Coulomb’s constant is k = 9×109 N·m2·C-2 Ans.: 4) A wire has a diameter of d = 100 mm, the length l = 314 m, and the resistivity ρ = 2×10-8 Ωm. Find the resistance R. Ans.: 10) The solenoid consists of a helical winding of wire on a cylinder, usually circular in cross section. The solenoid has n = 107 turns of wire per meter of length and carries a current I = 10 A. Find the magnitude of magnetic field B at the center of the solenoid’s length. Ans.: 5) Find the equivalent resistance, when the three resistors R1 = 8 kΩ, R2 = 20 kΩ, and R3 = 40 kΩ are connected in parallel. Ans.: 11) The speed of sound at 20 °C is υ = 344 m/s. The frequency is f = 86 Hz. Find the wavelength λ. Ans.: 6) Find the work of electrical forces A in uniform electric field with magnitude E = 1 N/C at displacement L = 1 km of charge q = +103 mC in the direction of the field. Ans.: 12) Find the underdamped response of the oscillator x at a moment in time t = 2 s if damping coefficient is g = 4 s-1, the amplitude is A = 10 m, the period is T = 1 s, the starting point (phase) is α = 0 on the cosine fashion. Ans.: Ans.: 4