Prokofiev VL - the solution of the entire version 09 on

Task 2.9
Two balls weighing 2 mg are suspended at a common point on filaments 0.5 m long. The balls were reported to charge and
Separate the filaments by 90 °. Determine the strength and potential of the field in the point of suspension of the ball.

Task 2.19
A charge of -1 nC was moved to the charge field +1.5 nC from a point with a potential of 100 V to a point with potential
600 V. Determine the work of the field forces and the distance between these points.
Task 2.29
The energy of a flat air condenser is 0.4 nJ, the potential difference on the plates is 600 V, the area
Plates 1 cm2. Determine the distance between the plates, the strength and the volume density of energy
Fields of the capacitor.

PROBLEM 2.39
To the current source, connect the resistor once with a resistance of 1 ohm, another time - 4 ohms. In both
The same amount of heat is allocated to the resistors at the same time. Identify
Internal resistance of the current source.

Task 2.49
The current flows through the square frame 4 A. The magnetic field strength in the center of the frame is 45 A / m. Identify
Perimeter of the frame.

PROBLEM 2.59
On rectilinear long parallel conductors, located at a distance of 2 cm, in one
1 A current flows. What work per unit length of conductors must be done to
Extend them to a distance of 4 cm?
Task 2.69
A single-layer solenoid without a core of 20 cm in length and 4 cm in diameter has a dense winding of copper
Wire diameter of 0.1 mm. For 0.1 s, the current in it decreases uniformly from 5 A to 0. Determine
Electromotive force induction in the solenoid.

Task 2.79
According to the winding of the solenoid with parameters: number of turns - 1000, length 0.5 m, diameter - 4 cm; Current flows 0.5A.
The dependence B = f (H) for the core is shown in Fig. 4. Determine the flux linkage, energy and
The volumetric energy density of the solenoid.