The circuit shown in is made of a homogeneous wire of constant cross section.

Find the ratio $\frac{Q_{12}}{Q_{34}}$ of the amounts of heat liberated per unit time in conductors $1-2$ and $3-4$.

The voltage between the anode and the cathode of a vacuum-tube diode is $U$ and the anode current is $I$.

Determine the mean pressure $p_{\mathrm{m}}$ of electrons on the anode surface of area $S$.

across the capacitor plates varies as shown in the figure Plot the time dependence of voltage across the clamps $CD$.

Two batteries of emf ${\epsilon }_1$ and ${\epsilon }_2$, a capacitor of capacitance $C$, and a resistor

of resistance $R$ are connected in a circuit as shown in Fig. 

Determine the amount of heat $Q$ liberated in the resistor after switching the key $\overrightarrow{K}$.

An electric circuit consists of a current source of emf $\epsilon$ and internal resistance $r$, and two resistors connected in parallel to the source (Fig.). The resistance $R_1$ of one resistor remains unchanged, while the resistance $R_2$ of the other resistor can be chosen so that the power liberated in this resistor is maximum.

Determine the value of $R_2$ corresponding to the maximum power.

A capacitor of capacitance $C_1$ is discharged through a resistor of resistance $R$.

When the discharge current attains the value $I_{0,}$ the key $K$is opened.

Determine the amount of heat $Q$ liberated in the resistor starting from this moment.

Find the amount of heat $Q$ liberated in the resistor after the key $K$ is switched.

In the circuit diagram shown in Fig. 105 , the capaeitor of capacitanco $C$

is uncharged when the key $K$ is open. The key is closed over some time during which the capacitor becomes charged to a voltage $U$. Determine the amount of heat $Q_2$ liberated during this time in the resistor of resistance $R_2$ if the emf of the source is $E$, and its internal resistance can be neglected.

A jumper of mass $m$ can slide without friction along parallel horizontal rails separated by a distance $d$. The rails are connected to a resistor of resistance $R$ and placed in a vertically uniform magnetic field of induction $\overrightarrow{B}$. The jumper is pushed at a velocity $v_0$.

Determine the distance $s$ covered by the jumper before it comes to rest. How does the direction of induction $\overrightarrow{B}$ affect the answer?