If a 120-volt, 50 watt lamp is connected in series with a 120-volt, 75-watt lamp, and the series circuit is supplied with a 240-volt source, the lamps will operate at their rated power outputs.True / False.

Respuesta :

Answer:False

Explanation:

Given

Power of first lamp  [tex]P=50\ W[/tex] at [tex]V=120\ V[/tex]

Power of second lamp [tex]P=75\ W[/tex] at [tex]V=120\ V[/tex]

Resistance of two lamps is given by

[tex]R=\frac{V^2}{P}[/tex]

[tex]R_1=\frac{120^2}{50}[/tex]

[tex]R_1=288\ \Omega[/tex]

For [tex]R_2=\frac{120^2}{75}[/tex]

[tex]R_2=192\ \Omega[/tex]

If both the lamps are connected in series with 240 V source  then the current in the circuit is

[tex]i=\frac{V}{R}[/tex]

[tex]i=\frac{240}{192+288}[/tex]

[tex]i=0.5\ A[/tex]

Power of first lamp [tex]P_1=i^2R_1[/tex]

[tex]P_1=(0.5)^2\times 288[/tex]

[tex]P_1=72\ W[/tex]

[tex]P_2=(0.5)^2\times 192[/tex]

[tex]P_2=48\ W[/tex]

Thus both operate at lower range of rated power