Download Electrical Circuits part 2

Electrical Circuits part 2 Objectives
1. Distinguish between a Series Circuit and a Parallel Circuit
2. Use Ohm’s Law to calculate the resistance and the voltage needed in a circuit.
3. describe how fuses, circuit breakers and grounding works to protect people from electric hazards.
Electrical Circuit Types
--An Electric Circuit is a pathway for electrons to travel to a (+) pole from the (-).
--There are 2 main circuit types, based on _______________________________________; Series and Parallel.
1. Series Circuit
--A series circuit ____________________________________ to travel from a
Power Source’s (-) to (+) .
--_______________ in the circuit ________________________________,
since there is only 1 electrical path.
--Ex: old Christmas Lights—one light burns out, they
all go out. (burned-out light breaks the circuit).
2. Parallel Circuit.
--A circuit that has ______________________________________ to travel from the
Power Source’s (-) to the (+) pole.
--A _________ in a Parallel Circuit _________________________________ because
there is _____________ ways for the electrons to get to the Circuit’s _______ pole.
--Ex: New Christmas Lights continue to work, even if a light burns out since there are
multiple ways for current to flow.

Ohms’ Law
Ohm’s Law
Moving electricity needs to _________________________—the more resistance in the wire, the more Power is needed
to overcome the resistance from friction--The _______________________ is used by engineers to
____________________________ in electrical devices.
Ohm’s Law states that the ______________ of an electric current in a circuit is directly __________ to the _________
and its ____________ --The _______________ in the circuit is measured units called _________
Using Ohm’s Law, you can calculate…
A. How much resistance you need to control the voltage
B. What speed (amps) the current will move
C. How much voltage is needed to power a circuit.
The equation can also be used to find the initial Voltage if the Resistance and Amps are known…
Voltage = Amps x Resistance
Ohm’s Law how-to
Ohms’ Law: Sample problem 1 The current in a hand-held video game needs to move at 0.5 A, with 120 V of power.
How much Resistance is needed protect this circuit?
Step # 1: list the knowns given from the problem….
1. Voltage = ______________
2. Amps/current =_____________
3. Resistance = ?
Step # 2: Use the proper equation to solve, and do the Math…
Resistance = Voltage / Amps 
________ / _________ = ___________
Step # 3: add the proper unit to your answer….
So a device that runs on 120 Volts @ 0.5 Amps needs ______________________ of resistance to protect it.
Ohms’ Law: Sample problem 2: How much electrical power (voltage) to power the circuits of a robot if it needs 2 amps
of current, and has 100 Ohms of resistance in its wires ?
Step #1: List the knowns from the problem…
1. Voltage = ?
2. Amps =______
3. Resistance = ______________
Step #2: Use the proper equation and do the math…
--Voltage = Resistance x Amps

_________ x _________ _______ = _______
Step #3: Finish with the proper Unit: _________________ of power would be needed to power the Circuits with 100
Ohms of resistance @ 2 amps.
On Your Own Ohms problems
1. How much Resistance (ohms) would be needed
control 110 V @ 0.2 amps?
2. A machine needs current to run at 0.6 amps to safely
and has 10 Ohms of resistance in its circuits. How
many volts would you need to power it?
Electrical Safety: objective:
1. describe how fuses, circuit breakers and grounding works to protect people from electric hazards.
Circuit breakers and fuses
--When ______________________ enters a household circuit (Power Surge) the circuit has ____________________ and
___________ that protect appliances/wires from fires.
--Electrical fires are caused when _____________ in the circuit changes
some of the electron’s ____________________ into _______________.
--The __________ the current moves, the ______________
is produced.
--Fuses and Circuit Breakers use this ___________________________
in the event of an electrical overload.
1. Fuses
--Circuit part made from a thin metal strip with a
_____________________________.
--If ________________________________ crosses the metal in the fuse, the
metal strip will ____________ and _______________ the circuit, stopping the
electrical current.
2. Circuit Breakers
--Circuit part made from a ____________________ that is held in place by a _______________________.
Or they use ____________________________________
--____________________________will cause the
bi-metal strip to __________________, breaking the
circuit, and ________________________ the power.
Electromagnetic breakers work when high current
________________________________________________and
stronger until the magnet can ____________________________________________________.
Grounding
--too much electrical power can also be _____________________________
completely to protect it. This is called _______.
---Grounding a circuit gives __________________________ that
____________ electricity where it wants to be—
__________________________.
--_________________________ are placed on tall buildings
________________________ against lightning strikes.
An attached wire carries the current safely into the ground.
--Some electrical plugs have a _______________ that grounds them
and will______________________ in case of accidents.
Lastly, metal Faraday Cages can be used to protect sensitive devices from
static electricity, and other current by ________________________________________.
Section 2 review
1. Draw a Series and Parallel Circuit in the space below.
2. What do electrical engineers use Ohm’s Law for? (there are 3 different answers)
3. Solve for ?:
A. Amps = 4
B. Amps = ?
C. Amps 3
Voltage = 100
Voltage = 9
Voltage = ?
Resistance ?
Resistance = 3 ohms
Resistance = 12 ohms
4. How does a fuse protect your stuff from damage during an electrical overload?
5. How is a circuit breaker different than a fuse?
6. How can a simple metal rod attached to a tall tower protect it from the high electric current of lightning?