AVE = 81

Review: the resistor

R

HW4 up – due monday

R

IRV

V decreases in the direction of (conventional) current flow

Review: the resistor

Batteries!

The perfect battery

ETV

E

Batteries!

A Perfect battery: loaded

ETV Still !

RI

E

E

Batteries!

V

A real battery

ETVE

Batteries!

V

A real battery: loaded

ETV

R

VI T

Term

inal

vol

tage

Current drawn from battery

E

TV

I

V

r

E

Equivalent circuit for a real battery

E

Real battery Equivalent circuit

How’s it work?

r

ETV

How’s it work?

TV

I

I

IrVR

E

Term

inal

vol

tage

Current drawn

E

rIVT E

I

Example: Lets measure E and r!

VDC

12.2 V

r

E

R

Example: Lets measure E and r!

ADC

10.6 A !

r

E

0R

What’s battery’s internal resistance?

?E

V2.12E

V2.12TV

A6.10I

Equivalent resistance

Equivalent resistance

Equivalent resistance

R

?

Series resistors

Not Yet!

I I1R 2R

V

Series resistors

now

21

21

III

VVV

1R 2R

I

1V 2V

I

Series resistors

1R 2R

21 RRREQ

EQR

Example: what’s the equivalent resistance?

5610 22 10 100

Parallel resistors

Not Yet!

1R

2R

V

I I

Parallel resistors

1R

2R

I I

1I

2IWhat to do?

Not Yet!

Parallel resistors

1R

2R

I I

1I

2I

now

21

21

III

VVV

Parallel resistors

21

111

RRREQ

1R

2R

EQR

Example: what’s the equivalent resistance?

56

10

22

10

Now try this!!!

5610

22

10 10

56 56

?EQR

Apply our rules in steps ….

Now try this!!! ?EQR

5610

22

10 10

56 56

Series resistors!

Now try this!!!

66

22

20

112

?EQR

Now try this!!! ?EQR

66

22

20

112

Parallel resistors!

Now try this!!!

0.9112

?EQR

Now try this!!!

0.9112

?EQR

Series resistors!

Now try this!!!

121

121EQR

12V

100

200

EXAMPLE: What’s the voltage across, and the current thru each resistor?

Not Yet!

12V

100W

200W

EXAMPLE: What’s the voltage across, and the current thru each resistor?

EXAMPLE: What’s the voltage across, and the current thru each resistor?

12V 100 200

EXAMPLE: What’s the voltage across, and the current thru each resistor?