Pick a topic on the left, open a problem and check the solution hint by hint.
An oil drop of mass $m = 2.4 \cdot 10^{-15}$ kg is in equilibrium between the horizontal plates of a parallel-plate capacitor. The distance between the plates is $d = 1$ cm, the voltage is $U = 500$ V, and the upper plate is positively charged (see the figure). Find the charge of the drop,…
Two capacitors of capacitances $C_1 = 2$ µF and $C_2 = 3$ µF are connected in series to a voltage source $U = 100$ V (see the circuit). Find the capacitance of the combination, the charge on each capacitor and the voltage across each of them. The capacitors were uncharged before the connection.
A resistor $R_1 = 4$ Ω is connected in series with two resistors $R_2 = 6$ Ω and $R_3 = 3$ Ω connected in parallel (see the circuit). A voltage $U = 24$ V is applied to the ends of the whole section. Find the current in each resistor and the voltage across $R_1$.
Positive point charges $q_1 = 12$ nC and $q_2 = 16$ nC are placed at vertices $A$ and $B$ of a right triangle $ABC$ with the right angle at $C$ and equal legs $CA = CB = a = 6$ cm. A positive point charge $q_0 = 1$ nC is placed at vertex $C$ (see the figure). Find the magnitude of the force acting…
A horizontal rod of mass $m = 40$ g and length $L = 50$ cm lies on two smooth parallel rails inclined at an angle $\alpha = 45°$ to the horizontal. The system is in a uniform magnetic field with a vertical induction vector $B = 0.2$ T (the figure is a side view, the rod is shown as a circle). What…
A ball of mass $m = 2$ g hanging on a light silk thread is placed in a horizontal uniform electric field of strength $E = 10$ kV/m. The ball is deflected and the thread makes an angle $\alpha = 45°$ with the vertical (see the figure). Find the charge of the ball (magnitude and sign) and the tension…
Find the work done by an electric current in a time of $t = 5$ minutes at a voltage of $U = 220$ V and a current of $I = 2$ A.
A source with emf $\varepsilon = 12$ V and internal resistance $r = 1$ ohm is connected to a resistor $R = 5$ ohm (the current in the circuit is $I = 2$ A). Find the voltage across the external part of the circuit.
A current source with emf $\varepsilon = 6$ V and internal resistance $r = 0.5$ ohm is connected to a resistor. The current in the circuit is $I = 4$ A. Find the resistance of the resistor.
A source of emf $\varepsilon = 12$ V with internal resistance $r = 1$ ohm is connected to an external resistance $R = 5$ ohm. Find the current in the circuit.