What is value of [3(_2_7÷(1.5+0.5)
Answers
Answer:
ANSWERS to CIRCUITS
1. The speed with which electrons move through a copper wire is typically 10-4 m s-1
.
a. Explain why is it that the electrons cannot travel faster in the conductor?
b. Explain why the electron drift produces heat?
1. a) collisons with the crystal lattice atoms b) collisions with lattice atoms transfers energy.
2. Explain in terms of atomic and electron movement, why resistance increases with temperature.
2. Electrons drift through the lattice, as temperature increases the lattice atoms vibrate more and this increases the probability of
collision and hence resistance to electrons has increased.
3. Calculate the resistance of an aluminum (ρ = 2.8x10-8 Ωm) wire that is 2.0 m long and of circular cross section
with a diameter of 1.5 mm.
3. 32 mΩ
4. Determine the length of tungsten (ρ = 5.6x10-8 Ωm) wire with a diameter of 1.0 mm that is used to make a 20.0 Ω resistor.
4. 280 m
5. A nichrome (ρ = 100x10-8 Ωm) wire has a diameter of 0.40 mm. Calculate the length of this wire needed to carry a current
of 30 mA when there is a potential difference of 12 V across it.
5. 50 m
6. A thin copper (ρ = 1.68x10-8 Ωm, but you don’t need it) wire 200 cm in length has a 9 V dry cell connected between its ends.
Determine the voltage drop that occurs along 30 cm of this wire.
6. 1.35 V
7. If the potential difference across the bulb in a camping lantern is 9.0 V, what is the potential difference across the battery used to
power it?
battery gives the voltage of 9.0 V to the lantern to use it.
8. How much current, in amperes, is in a lightning stroke that lasts 0.05 second and transfers 100 coulombs?
I = q/t = (100 C)/(0.05 s) =2000 A
9. Calculate the resistance of the filament in a light bulb that carries 0.4 A when 3.0 V is impressed across it.
V = IR R = V/I = 7.5 Ω
10. Electric socks, popular in cold weather, have a 90-ohm heating element that is powered by a 9-volt battery.
How much current warms your feet?
V = I/R = 0.1 A
Step-by-step explanation: