june 6 2011

READ PAGES 15-20!!!

DO PAGES 48-50!!!

finish page 14

Answer keys:

page 29

1) P=v^2/R

= (3)^2/30

= 0.3 W

2) T=v/R

=3/30

=0.1 A

3)power varies inversely with resistance. as R of bulb increases the amount of power of the bulb increases

4) E(or W)=Pt

= (.3)(3600)

= 1000J

page 31

1. resistance- property of an object that determines how much current will flow through that object

factors- length of the wire cross sectional area temperature material the object is made of.

2. voltage is a potential difference in other words voltage is PE/ charge. current is the movement of charge due to potential difference. thus, voltage is nothing more than a difference in potential and does not necessarily create a current. given the proper conditions, voltage causes charge to move and when they do a current is created

3. R=v/I

since v is a constant and R is increasing, the circuit must be decreasing

4. they allow complex circuits to be graphically illustrated clearly and concisely

June 2nd

Worked on Pages 44,45,46, and 48
Pages 5- 12

Notes:

An electric current is a flow of charged particles.
A conventional current is just a flow of a positive charge.
Charges can not be created or destroyed, but they can be seperated.
A resistor is a device designed to have a specific resistance.
Resistance is known as the ratio of potential difference to the current.
Temperature can increase resistance since a moving charge is affected by molecules, greater molecular motion would thus increase the resistance.

Formulas:

I = q/t
I is the conventional current measured in Amperes (A)
q is the charge measured in Coulombs (C)
t is the time measured in seconds (s)

P = IV
P is power measured in Watts (W)
V is the Potential Difference also reffered to as Voltage, it is measured in Volts (V)

R = V/I
R is the resistance, measured in ohms, the symbol omega (Ω) can be used to represent it.

R = pL/A
p is a constant(the resistivity of the metal) (Ω·m)
A is the crossectional Area (m^2)
L is the length of the material (m)

Useful Ratios to take note of:

R1/R2 = L1/L2
R1/R2 = A2/A1
R1/R2 = p1/p2

For P46

Nichrome wire resitivity at room temperature varies from 1.10 × 10−6 Ω*m to 1.5 × 10−6 Ω·m
Tungston wire resistivity at room temperature is 5.28 × 10−8 Ω·m

May 31

Today we were given our exam reviews and also started our new unit on electricity.

We preceded the unit with a lab; using a light bulb, wire and a 'big' battery, we were to find a few ways on how to light the bulb, and a few ways where we couldn't. We were to illustrate the circuit diagrams in our hand-out booklet on the back page of the lab.

Within the booklet, we were to read pages 5 to 12 and were to do worksheets 44,45 & 46.

The current, I, is measured in C/s and is represented by the unit A, amperes.

Potential Difference, V, is measured in J/C.

Power, P, is measured in J/s and is represent by the Watt, W.

I=q/t V=E/q P=IV E/t=IV

P=(q/t)(E/q)=E/t

P=(1 C/s)(1 J/C)=1 J/s

Please feel free to correct.