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Electric Circuits

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There are two different types of electrical circuits.

Series

Parallel

and

More than 1 path

One Path

Circuit in which a current flows through each component, one after another. There is only one path for the current to follow.

Current

Because there is only one path for electrons to travel in a series circuit. The current at any one point in the circuit would be equal to the current at any other point in the circuit.

The current through each resistor is the same.

Resistance

Once again because there is only one path in a series circuit, for the case of resistance this means that each electron will have to go through every resister with in the circuit.

Therefore the total resistance is the sum of all the resistors found in the circuit.

Potential Difference (Voltage)

In the picture above, the skate boarder has a drop in gravitational potential energy at each stage during the trip.

This is very similar the drop in electric potential energy (voltage) in a series circuit as an electron passes through a resister.

In a series circuit the total voltage drop across the entire circuit is equal to the sum of the individual voltage drops across each resister.

2V

4V

6V

12V

Example:

What would the potential difference be across the second resister?

4 Volt Drop

http://www.stmary.ws/highschool/physics/home/animations3/electricity/circuits2_bigger.swf

Example:

Find the total current in the circuit below.

Four loads (3.0 , 5.0 , 7.0 , and 9.0 ) are connected in series to a 12 volt battery.

a) Find the equivalent resistance of the circuit.

24

b) Find the total current in the circuit.

0.50 A

c) Find the potential difference across the 7.0 load.

3.5 V

Circuit in which there are two or more paths for the current to flow.

Here’s A Thought

Picture walking through a crowded building, and there are that many people that you can hardly move. Then the hallway splits into two hallways of the same size. Half the people go one way and the other go the other way.

Now you have much more room because there are only half as many people in the hallway.

What would happen if the hallway was to split again? And again?

Would you have more and more room to walk each time?

If you have more room would it be easer for you to walk down the hallway? Could you say that there is less resistance to your motion?

This is what happens within a parallel circuit, the more paths that electrons have to chose from, the less over all resistance there is to their motion.

In a parallel circuit the total resistance can be found by the following formula

If each resister is 6 Ω, then we get

Because the current had 3 equivalent paths to chose from the over all resistance is 1/3 of what it would have been otherwise.

Find the total resistance of the given parallel circuit

50Ω

100Ω

250Ω

Not how the total resistance is smaller than any of the individual resistors.

In a parallel circuit the total current is equal to the sum of all of the individual currents through each branch of the circuit

3 A

2 A

3A

5 A

In a parallel circuit the total current is equal to the sum of all of the individual currents through each branch of the circuit

What would the voltage be across a resister that was hooker up at any location between the two wires?

In a parallel circuit the total voltage is the same as the voltage across each individual resistor.

Hook up a wire to each terminal

Measure the voltage anywhere between the two wires

12V

12V

12V

12V

Take a 12 volt battery.

http://www.stmary.ws/highschool/physics/home/animations3/electricity/circuits2_bigger.swf

Find the total current of the given parallel circuit

Solve the following circuit.

A 60 V battery is connected to four loads (3.0 , 5.0 , 12.0 , and 15.0 ) in parallel.

a) Find the equivalent resistance of the circuit.

1.46

b) Find the total current leaving the battery.

41.0 A

c) Find the current through the 12.0 load.

5 A

DO

Pg. 719 #’s 27 – 31 (pdf 89)

- Pg. 724 #’s 32 –35 (pdf 89)

A complex circuit is one that has both series and parallel components at the same time.

Despite their name, the method for working with complex circuits is quit easy. We simplify the circuit into a smaller less complicated circuit, one section at a time.

The first thing we see here is 3 different series circuits (which can be simplify) embedded within the complex circuit.

Now we have a plane parallel circuit that we can easily work with.

Example:

- Find the equivalent resistance of the circuit below.

- Step 1: Combine the 2 resisters that are in parallel.

- Step 2: Combine the 3 resisters that are in series.

- Step 3: Combine the 2 resisters that are in parallel.

- Step 4: Combine the 2 resisters that are in series.

DO

- Pg. 728 #’s 36 & 37 (pdf 89)

- Pg. 733 #’s 1-7 (pdf 89)

RRHS Handout

- Do Your Ohm Work