Download presentation

Presentation is loading. Please wait.

Published byEstefany Hawken Modified over 2 years ago

1
From last lesson we found… VOL = distance x Area = speed x time x Area # ELECTRONS = charge/charge of 1 electron = current x time / e NUMBER DENSITY, n = # electrons/vol n = (I x t)n = I/evA e x v x t x A nAve = I

2
The big question: What did Kirchoff say? Why are we learning this? Supermax (super maximum security) prisons e.g. Alcatraz

3
Learning Objective: To evaluate Kirchoff’s first law The big question: What does Kirchoff say? A – B – C – D -

4
Calculate velocity A copper wire has cross-sectional area 3.0 mm 2 and current 5.0A. Copper’s number density is 6.0x10 28 m -3. A brass wire has cross-sectional area 6.0mm 2 and current 9.0A. Assume Brass’s number density is 9.0x10 28 m -3. A brass wire has radius ½ that of the previous question, with the same current.

5
On a whiteboard: (b) A silver wire has cross-sectional area 3.0 mm 2 and current 2.0A. Copper’s number density is 4.0x10 28 m -3. (A) If the radius was ¼ as small, then the number of electrons will be what factor smaller?

6
Learning Objective: To combine knowledge on density and electricity to calculate velocity The big question: How do we combine density with velocity? A – Predict insulator number densities B – Analyse how number density changes drift velocity C – Create a formula for drift velocity and Current D – Calculate drift velocity

7
Calculate mean drift velocity: A copper wire has cross-sectional area 4.0 mm 2 and current 5.0A. Copper’s number density is 8.0x10 28 m -3. A brass wire has cross-sectional area 6.0mm 2 and current 15.0A. Assume Brass’s number density is 9.0x10 28 m -3. (C) Using letters n for number density, I for current, e for charge of 1 electron and A for cross-sectional area, write an expression for v

8
What do they do? A – Predict insulator number densities, using your expression from C and B B – Analyse how number density (n) changes drift velocity. Keep all other numbers the same and change n up and down, to see the effect on velocity C – Create a formula for drift velocity, v and rearrange it for current, I

9
Current, I = nA/veve/nA n/vAenAve

10
If the wire had a high number density V is velocity v would increasev would stay the same v would decrease

11
If the wire was an insulator number density number density would increasewould decrease number density would stay same

12
Learning Objective: To combine knowledge on density and electricity to calculate velocity The big question: How do we combine density with velocity? A – Predict insulator number densities B – Analyse how number density changes drift velocity C – Create a formula for drift velocity and Current D – Calculate drift velocity

13
Learning Objective: To combine knowledge on density and electricity to calculate velocity The big question: How do we combine density with velocity? A – Predict insulator number densities B – Analyse how number density changes drift velocity C – Create a formula for drift velocity and Current D – Calculate drift velocity

Similar presentations

OK

Selected Problems Tutorial # 2. 1. One end of an Al wire (diameter 2.5mm) is welded to one end of a Cu wire (diameter 1.8mm). The composite wire carries.

Selected Problems Tutorial # 2. 1. One end of an Al wire (diameter 2.5mm) is welded to one end of a Cu wire (diameter 1.8mm). The composite wire carries.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on ict in higher education Ppt on selling techniques Ppt on central limit theorem formula Download ppt on space exploration Ppt on obesity management services Ppt on intelligent manufacturing Ppt on bluetooth based smart sensor networks pdf Ppt on db2 mainframes cics Ppt on forensic science laboratory Ppt on recycling of wastes