Chapter 17

Question 1

What is the direction of current?

Answer 1

Opposite to the direction of motion of electrons
The electrons lose energy as they move along the wire and energy lost is transferred to the wire
Slides 10 and 11 Nov 23

Question 2

What is the rate at which energy is transferred to the wire?

Answer 2

Pav= qΔV/Δt
Pav= Iav (V)

ΔV= potential difference

Slide 13 Nov 26

Question 3

What does a lightbulb turn on instantly when electron drift speeds are a fraction of a millimeter per second?

Answer 3

Because there are already electrons in the wire to be pushed

Question 4

How is an ammeter and a voltmeter places in a circuit and what does each do?

Answer 4

Ammeter- places in series to measure current
Should have small resistance
Voltmeter- placed in parallel and measures potential difference
Should have large resistance
Slide 22 nov 23

Question 5

Why is there smaller electric current in a longer conductor?

Answer 5

longer conductor means Smaller electric field means less force on electrons and smaller drift speed and therefore smaller electric current

Ratio on slide 32 Nov 23

Question 6

How do you know if α is negative or positive?

Answer 6

Mostly positive because higher temp means higher atomic vibration and higher resistivity
Negative when it’s a semiconductor since an increase in the number of charge carriers with higher temperature

Question 7

What is super conductivity?

Answer 7

Quantum mechanical effect that occurs in some materials at very low temps
In conventional superconductors, electrons move together in cooper pairs and are unaffected by interactions with atoms of material which makes electrical resistance zero