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ELECTRICITY IES RĂ­o Cabe

1) ELECTRICITY AND MATTER. 1.1. Conductor and insulators Covadonga Yugueros 1.2. How to obtain electricity Valbuena 1.3. The transport of electric energy 1.4. Effects of electric current 2)Electric quantities 2,1. Electric current 2.2. Voltage 2.3. Resistance. 3) Ohm's law 4)Electric circuits 4.1. Components of an electric circuit 4.2. Representation and symbols. 5)Types of circuits. 5.1. Series circuits 5.2. Parallel circuits 5.3. Series-parallel combination circuits


5. Types of circuits There are lots of different ways to connect components in a circuit

The most common connections:

Series circuits

Parallel circuits


5,1. Series circuits

-

+

Components are placed one after the other in the circuit. There is only one possible path for the electric current to flow through


Series circuits The same current flows through all the components

The total resistance is the sum of all the resistances R1

R2

R3

Rtotal = R1 + R2 + R3

The voltage of the battery is the sum of the voltages of all the receptors in the circuit.: B1

B2

V2

V1

V total +

B3

V3

Vtotal = V1 + V2 + V3


Series circuits If one of the components stops working, none of them will work because the circuit will be open.

+

+

9V

9V

+

9V

Batteries en series: If we connect some batteries in serie, the total voltage is the sum of the voltage in each battery +

+

+

3V

1,5V

+

1,5V

1,5V

4,5V

+

1,5V

1,5V

Batteries in series: The negative pole of one battery with the positive pole of the next one.


Series circuits Fuses and control elements are always connected in series with the receptors that must be protected or controlled.

Control element +

Fuse

-

Practice Series Circuit

Practice2 Series Circuit


Example of a series circuit:

In the following circuit calculate: * The total resistance

R1

R2

50 立

100 立

30 立

* Total current * Voltage on each receptor.

+

9V

a

b

c

Rtotal = R1 + R2 + R3 Ohm's law

Itotal = VTotal /RTotal

In a series circuit the current is the same in all elements.

Ohm's law in each component

V1 = R1 * I V2 = R2 * I


5,2. Parallel circuit The components are connected on different branches of the wire. There are several possible paths for the electric current to flow through

+

ram +

-

Dia g


Parallel circuit

The intensity is shared by all the possible paths The current will be higher

As lower be the resistance Itotal

I2

Total current is the sum of the intensity in each branch

I1 +

Itotal

10 立

5立

I1

I2

Itotal = I1 + I2 Itotal = I1 + I2 + I3


Parallel circuits

Voltage is the same in Vtotal

+

each branch

V1

V2

Vtotal = V1 = V2 We can calculate the total resistance using this formula R1

100 立

1

Rtot

=

1 1 R1 + R2

1 1 1 1 Rtotal = R1 + R2 + R3 1

Rtot

R2

100 立

1

Rtot +

9V

=

1 50

Rtot = 50立

=

1 100

+

1 100

=

2 100


Parallel circuits If one of the components in parallel stops working, the rest continue to work because the electric current takes another path.

+

+

+ 9V

9V

9V

Batteries en parallel: Poles of the same sign are joined together. These batteries must have the same voltage, and the circuit is equivalent to having another battery of the same voltage but longer. 1,5V

1,5 V

+

+ +

1,5V


Parallel circuits If a wire is in parallel with a receptor, this will not work, because the current will choose the path that less work required.

This is a short circuit +

Lamp is in a short circuit

+

Practice 1 Parallel Circuit Practice 2 Parallel Circuit


Example of a parallel circuit:

In the folllowing circuit claculate:

12 立

6V

* Total resistance

M

+

* Total current * Voltage and current in each component.

a

b

c

1 1 1 1 Rtotal = R1 + R2 + R3 Ohm's law

Itotal = VTotal /RTotal

In a parallel circuit the voltage is the same for all elements.

Ohm's law in each component

I1 = V/R1 I2 = V/R2

6立


5,3. Series-parallel combination circuits These circuits contain devices connected in series and in parallel

B1

B2

+

-

B3

Di ag

ra m B1

+

B3

B2


Series-parallel combination circuits In the following circuit analyze what elements are in series and which are in parallel. B1 is in series with the parallel of B2 - B3

B2 y B3 are in parallel

B1

+

B2

B3

9V

B2

B1

M

B1 y B2 are in series

Motor is in parallel with B1 - B2

+


Electricity: types of circuits