# How to Verify the Maximum Power Transfer Theorem for DC

• 1). Write down and consider the case where the load resistance is equal to the internal resistance of the source:

EMF of the source Vs = 6 V.

Internal resistance of the source Rs = 1 ohm.

Resistance of the load Rl = 1 ohm.

Current in circuit Ic = Vs / Rs + Rl.

Ic = 3 A.

Power in watts W in Rl = Ic^2 x Rl = 9 W.

• 2). Write down and consider the case where the load resistance is half of the the internal resistance of the source:

EMF of the source Vs = 6 V.

Internal resistance of the source Rs = 1 ohm.

Resistance of the load Rl = 0.5 ohm.

Current in circuit Ic = Vs / Rs + Rl. = 6 / 1 + 0.5

Ic = 4 A.

Power in watts W in Rl = Ic^2 x Rl = 8 W.

Note that the power dissipated in the load resistor decreases as its value decreases below the that of the source internal resistance.

• 3). Write down and consider the case where the load resistance is double the internal resistance of the source.

EMF of the source Vs = 6 V.

Internal resistance of the source Rs = 1 ohm.

Resistance of the load Rl = 2 ohm.

Current in circuit Ic = Vs / Rs + Rl. = 6 / 1 + 2

Ic = 2 A.

Power in watts W in Rl = Ic^2 x Rl = 8 W.

Note that the power dissipated in the load resistor decreases as its value increases above that of the source internal resistance.