91影视

According to Ohm鈥檚 law, the voltage is directly proportional to R. So, in this case, the maximum voltage will be obtained when the resistance is infinity. At infinity, there is no current flow in the circuit.

$$\begin{gathered} V_{max}=鈭�-Ir \\ {V}_{max}=15V-0 \\ {V}_{max}=15V \end{gathered}$$

Therefore, the maximum voltage voltmeter reading is 15 V

According to Ohm鈥檚 Law, the current is inversely proportional to resistance. So, in this case, the maximum current will be obtained when the resistance is zero. At zero resistance, the flow of current in the circuit is maximum.

$$\begin{gathered} I_{max}=\frac{鈭�}{R+r} \\ {I}_{max}=\frac{15V}{0+4惟} \\ {I}_{max}=3.75A \end{gathered}$$

Therefore, the maximum ammeter reading is $3.75A$

The below graph shows the curve between the voltage and the resistance where the voltage increases as the resistance increases to infinity.

The below graph shows the curve between the current and the resistance where the current decreases as the resistance increases till the current reaches to zero.