Electrical Circuits: Understanding Voltage, Resistors, and Kirchhoff's Rules, Slides of Physics

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Direct

current

circuits

Voltage

and

resistor

circuits

Kirchhoff’s

rules

Equivalent

circuit

for

E

R

r

I

IR

Ir

E

E

E

=12V,

r=0.

R

what

is

V?

A.

V=

E

B.

V<

E

C.

V>

E

V

V

IR

V

A

A

I

Resistors

in

series:

2 1 2 1 2 1

0

R

R

R

R

R

V

I

IR

IR

V

series





 











Examples:

R

,^

R

,^

V=100V

V

IR

V

V

IR

V

A

R

R

V

I

IR

IR

V

(^01).

99

(^99). 0

(^99). 0

100101

0

2

2

1

1

2

1

2

1

















 











A

I

I

I

A

R

V

I

A

V R

I

R

I

V

R

I

V

2

1

2

2

1

1

2 2

1 1

Circuit

analysis

Kirchhoff’s

rules

Conservation

of

charge

(current)

at

a

junction:

0

0

3

2

1









I

I

I

I

junction

Example:

A

R

R

I

I

IR

IR

for

Solve

2

1

2

1

2

2

1

1

E

E

E

E

I <

means:

A.

The

circuit

is

wrong

(cannot

exist

or

will

blow

up).

B.

The

current

flows

opposite

the

arrow.

Docsity.com

Example:

I^3

I^2

3

2

1

3

1

2

3

I

I

I

I

I

I

I 

A

I

A

I

A

I

1 2 3

R

2 R

1

I     

that

Suppose

2

1

R

R

A

I

A

A

R R

I

I^

(^21)

2

Current

that

drives

measurement

device.

What

if

the

ammeter

were

connected

in

parallel

to

the

wire?

(Assume

that

the

wire

resistance

is

R

w

A

A.

The

measurement

would

be

identical

to

series

result.

B.

The

measurement

would

be

less

than

the

series

result.

C.

The

measurement

would

be

greater

than

the

series

result.

A

A

R R

R R

I

I

w

2

2 1

2

Total

equivalent

circuit:

Suppose

I

=10A,

R

eq

,^

R

=100 V

^ eq

V

V

eq

V

V

IR

R

I

IR

R

I

R

RV eq

I^

I

I^1

I^2

I^3

I^3

unknowns

need

equations

0

6 4

12

4

0

8

12

4

0

4

6

8

2

3

1

3

2

1

3

2

1



 













 









I

I

I

I

I

I

I

I

I