Transcript Electricity-Merit

Electricity Merit Badge
**Contains some graphic images.
What is Electricity?
A form of energy resulting from the existence of
charged particles (such as electrons or protons),
either statically as an accumulation of charge or
dynamically as a current
or
A physical phenomenon associated with
stationary or moving electrons and protons
*Volt: The unit of measurement for the
pressure or force of the electricity.
*Ampere: The unit of measurement for the
electrical current or the flow of
electrons.
*Resistance: The ability of an item to oppose
electrical current.
*Ohm(Ω): The unit of measurement for
resistance.
Ohms Law
V
I
• V= Volts
• I= Amperes(Amps)
• R= Ohms(Ω)
R
Ohms Law
V
I
R
• V= I *R Voltage= Current * Resistance
• I= V/R Current= Voltage / Resistance
• R= V/I Resistance= Voltage / Current
Req. 3
Build a Simple Electromagnet
Websites:
http://education.jlab.org/qa/electromagnet.html
http://www.energyquest.ca.gov/projects/electromagnet.html
Req. 4
Direct Current
• Current that flows in only one direction.
• Convenient as portable power.
• Good for short distances.
Req. 4
Alternating Current
• Current that reverses direction at a regular
rate (cycles).
• The cycles in the house are 60 Hertz or 60
cycles per second.
• AC is very useful for long distances.
• Power plants produce AC power to distribute
over long distances.
Req. 5
How a Battery and Bell Work
1. Switch is pushed and closes circuit
which creates current flow.
2. Current activates the electromagnet.
3. Electromagnet pulls the iron armature
and causes the hammer to strike.
4. As the armature is pulled, it is pulled
away from its contact point and opens
the circuit.
5. The current stops and deactivates the
electromagnet.
6. The armature returns back to its
original position and closes the circuit.
7. The cycle is repeated rapidly for as long
as the switch is pushed.
Contact
point
3-Phase AC Power
A power plant produces three different phases
of AC power simultaneously, and the three
phases are offset 120 degrees from each other.
The power plant produces thousands of volts
which go to the substation outside of the power
plant. Transformers at the substation step up
the voltage for long distance travel to 100,000700,000 volts.
• High-voltage
transmission lines.
• Large steel towers
• 3 sets of lines for 3phase.
• Ground wire on top of
towers for lightning.
• Transmission lines go to a small substation and the
voltage is stepped down to less than 10,000 volts.
• Power goes to the distribution bus. Power can be
stepped down to standard line voltage (7,200).
• Transformer steps down
voltage to 240 volts.
• 3 wires go to the
watthour meter.
• Bare wire is ground and
the other 2 wires are each
120 volts.
Req. 9
Watthour Meter
*Watt: The unit of electrical power(P). Rate of
work done which can be expressed as P = V * I.
Monthly electric bills are recorded in kilowatthours used. A kilowatt-hour is 1,000 watt-hours.
One kilowatt-hour equals 1,000 watts used in an
hour(or any equivalent such as 500 watts used
for two hours).
Req. 6
Fuse and Fuse Box
Circuit Breaker Operation
Ground Fault Circuit Interrupter
• GFCIs are used to prevent shock to someone. They sense an abnormal
difference in current from the hot and neutral wires in household circuits.
• They are designed to interrupt the circuit by detecting a few milliamps of
current compared to over 15 to 20 amps needed to trip a circuit breaker.
• Required to be installed in bathrooms, kitchens, and other places that
pose higher shock hazards such as some outside locations including near
swimming pools.
*Potential Difference: Commonly referred to as
voltage. It is the voltage between 2 points.
*Rectifier: Used to convert AC to DC.
*Rheostat: An adjustable resistor that is used to
vary the current(I). Dimmer switch.
*Conductor: Any material that will allow the
flow of current.
*Ground: 1. The common return to Earth for AC
power. 2. To connect a part of an
electrical system to ground.
*Circuit: A path through which current travels
from the source and through a device and
back to the source.
*Short Circuit: Sometimes referred to as a
Short. A shorter, low resistance
unintended path instead of passing
through the intended load. Bare wires
touching.
Complete the Following Requirements:
• Req. 2: Electrical Safety Inspection Checklist
• Req. 3: Make a simple electromagnet
• Req. 8: Bedroom floor plan
• Req. 9: Read an electric meter
• Req. 11: Do any TWO