Electricity Hand Outs

Electricity
1. Electricity – branch of physics that deals with the effects of flowing charges.
2. CIRCUIT – a closed conducting loop in which charged particles can move in one
direction.
3. Electric potential exist when electric charges in atom are separated.
 All conductors have free electrons that carry electrical energy around the circuit.
 Open circuit – there is a break in the circuit, then it is no longer closed conducting loop.
The flow of electrons immediately stop when there is a break in the circuit.
 Closed circuit - one in which the charges are flowing.
PARTS OF A BASIC CIRCUIT
1. Battery - an electrochemical cell; it converts chemical energy into electrical energy.

2. Load – to dissipate the energy of the moving charges.
- An electrical component that converts electrical energy into something useful.
Ex. A bulb converts electrical energy into light and heat.
3. Connecting wires – to hook up the load to the battery or potential source.
The most common connecting wire material.
COMMON CIRCUIT SYMBOLS
4. Electromotive force (emf) is the potential difference between the ends of the terminals of a
battery or cell.
5. The direction of current may be described in one of two ways:
A. Conventional current – current direction is from positive to the negative terminal of
the battery – opposite the direction of charges
B. Actual Current – current is from the negative to positive terminal of the battery,the
same as the direction of the flow of charges.
Three Important quantities

6. Voltage – the potential difference between two points in the circuit.
V represents voltage;measured in Volts (V) named Alexander Volta.
7. Current – the rate of flow of charges.
- I represents Current.
- Measured in Amperes (A),named after the French Physicist Andre – Marie
Ampere.
- Andre – Marie Ampere – honored for his work in electromagnetism.
8. Current being the flow of charges has direction of “DC” stands for direct current. Direct
current has one direction only. Everytime you use a battery powered device you use DC.
9. AC stands for alternating current is the one you use when you plug your electrical or
electronic devices to the power outlet on the wall.
10. Resistance - is the property of a conducting material that limits the flow of charges
through it. It is measured in Ohms(Ω).
11. Factors affecting the resistance of the wire
1. Length - electrons going through a long piece of wire encounter greater resistance
because they have to go through many collisions along the way than when the wire
is short.The longer the wire the higher is its resistance.
2. Cross sectional area – the resistance of the wire is inversely proportional to its cross
sectional area.The bigger the wire the lower is its resistance.
12. Ohm’s Law describes the relationship between current,voltage,and resistance in a circuit. It
only applies to Ohmic conductors or metallic wires. In symbols, Ohm’s Law is written as:
V = IR
13. Electricity can be harmful depending on the amount of current.Current depends on both
voltage and resistance. Factors such as geometry of a person’s body and the amount of
liquid and fat he/she has determine his/her resistance against the flow of current.
14. A resistor is a circuit component used to control or limit current.
15. Circuit devices or elements can be connected together in either series or parallel
connection.
16. When resistors are connected in series, the equivalent resistance is greater than the largest
resistance used. When resistors are connected in parallel,the equivalent resistance is
smaller than the smallest resistance used.
17. Cells may be connected together.When cells are connected in series, total emf is the sum
of the individual emfs. When cells are connected in parallel, the total emf is equal to the
individual emfs. Cells are connected in parallel should be identical.
18. The power dissipated in a circuit can be computed using any of the following equations:
P = IV or P = I²R or P = V²/R
19. The electrical energy E that an electrical device uses is equal to: E =Pt
Where P is the power in watts and t is the time in seconds. The resulting energy is E is in
joules
20. An overload occurs when the current in a wire is high enough to cause overheating and
melting and insulation.A fire may result when this occurs.
21. Fuses and circuit breakers cut off the flow of charges when it reaches an unsafe level.
22. Electrical shocks may be prevented by properly grounding home appliances and devices.

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Electricity

PARTS OF A BASIC CIRCUIT

1. Battery - an electrochemical cell; it converts chemical energy into electrical energy.

COMMON CIRCUIT SYMBOLS

Three Important quantities

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