Question

1. 50 W and 100 W lamps are designed for the same voltage. Which lamp has the higher filament resistance and why?

2. At a voltage of 4 V, 300 mA flows through the bulb. What is the work done by the electric current in 5 min?
3. The label on the lamp says 100 W, 220 V. Calculate the resistance of the lamp?
4. What is the work done by the motor of a floor polisher in 25 min with a voltage of 220 V, a current rating of 1,25 A and a motor efficiency of 80%?
help

Answer 1

Look below.

Step-by-step explanation:

1.) The resistance of a light bulb filament is effected by both length and cross-sectional area. Thicker wires have less resistance. A 120-Watt bulb has a greater current and a smaller resistance. Thus, a 120-Watt bulb must have a thicker filament than a 60-Watt bulb (assuming the lengths of the filaments are identical). We also think of lightbulbs in terms of their power ratings in watts. Let us compare a 25-W bulb with a 60-W bulb. Since both operate on the same voltage, the 60-W bulb must draw more current to have a greater power rating. Thus the 60-W bulb’s resistance must be lower than that of a 25-W bulb. If we increase voltage, we also increase power. For example, when a 25-W bulb that is designed to operate on 120 V is connected to 240 V, it briefly glows very brightly and then burns out. Precisely how are voltage, current, and resistance related to electric power?

2.) Energy transferred = 120 × 2 = 240 J. This equation can be rearranged to V = E ÷ Q. So voltage is energy transferred divided by charge.

3.) Power= Voltage × Current

4.) W=Pt