Physics Answers

A filament lamp operates at maximum brightness when connected to a 6.0 V supply. At maximum brightness, the current in the filament is 120 mA

A. (i) Calculate the resistance of the filament when it is operating at maximum brightness.

(ii) You have available a 24 V supply and a collection of resistors of a suitable power rating and with different values of resistance. Calculate the resistance of the resistor that is required to be connected in series with the supply such that the voltage across the filament lamp will be 6.0 V. 

Tommy runs his juicer every morning. The juicer uses 90 W of power and the current supplied is 4.5 A. How many volts are necessary to run the juicer? Ans: 20 V

If a clock expends 2 W of power from a 1.5 V battery, what amount of current is supplying the clock? Ans: 1.3 A

If a blender is plugged into a 110 V outlet that supplies 2.7 A of current, what amount of power is used by the blender?

A light bulb rated as 60 W at 220 V has a potential difference of 110 V across its ends. Find the power dissipated in the light bulb, assuming that the light bulb is ohmic (which it likely isn't). Ans: 15 W

A resistor of resistance 12 Ω has a current of 2.0 a flowing through it. How much energy is generated in the resistor in 1 minute?

The resistance in a fixed length of a wire of circular cross-section is 10.0 Ω. What will be the resistance of a wire of the same length made with the same material but with only half radius? Ans: 40 Ω

The resistivity is 1.68 x 10^-8 Ωm. Calculate the length of a copper wire with diameter 4.00 mm that has a resistance of 5.00 Ω. Ans: 3.74 km.

Calculate the total resistance of two, three, four and five 60 Ω resistors in parallel. What is the simple relationship for the total resistance of equal resistances in parallel?

Find the total resistance in each case:

a. A 16 Ω and an 18 Ω resistor connected in parallel

b. A 20 Ω, 10 Ω and 5 Ω resistor connected in parallel