Download Charge: Charge: Electrons, protons Unit of charge is Columbs

Charge:
Charge: Electrons, protons
Unit of charge is Columbs.
6.2415x1018 proton= 1C.
e= - charge, p=+ charge
Electric Potential= Voltage
Battery= Electrical devide that is made of seperating charges.
Voltage=Electric potential energy (J)/Charge(C)
+ and – cahrges are located at the baterry terminals.
Unit of voltage is volts (V)
Potential difference is dependent upon the charge difference between two points. Hence, it is also
called the potential difference.
1V is equal to 1J of energy done by 1C charge.
Electric current: The amount of charge moving in unit time.
The unit of electric current is Ampere (A).
1A is the flow of 1C of charge in 1sec.
Types of electric current:AC (Alternating current), DC(Direct current)
Conduction current occurs through the motion of electrons in a conductor.
Conductors and Insulators:
Conductors: contains lots of free charges.
Insulators: do not contain free charges, high energy is reqıired to seperate electrons for motion.
Semi-conductors.
Resistance:
Resistance is how much a matter opposes against the electric current.
Unit is ohms.
Resistance=R=l/(sigma xS)
Impedance: Resistance in AC circuits.
Electric circuit: is the connection of batteries and resistors through conducting wires.
Ohms law: In a closed electric circuit, V=IR
The power consumed in a resistor: P=IV (W)
The consumed energy(J)=Pxt
Electric current types:
Direct current : current that does not vary in time.
DC current always flows in the same direction in a conductor.
DC current is obtained from batteries.
Electric current types:
AC current: It is the current that changes in time periodically.
It is known as alternating current.
The amplitude changes as trigonometric function.
Definitions of AC current:
Period is the time it takes for the current to complete a full cycle.
Frequency is the amount of cycles in 1 sec.
The maximum value of the current or voltage is called the amplitude.
Power lines use 50 Hz, 220V amplitude voltage.
FM radio broadcasting uses 88-109 MHz AC current.
Mobile phones use 1GHz AC current.
Radars use 10-20GHz AC current.
Why do we use AC current in power lines ?
-
Easy to generate
Easier to transfer energy to long distances.
Installation Cost and line losses are less than that of DC.
It is possible to use transformers.
Electrical Energy generation:
Electrical energy sources: Renewable: sun, water, wind, .. Non renewable: (fossil based) coil, oil,
natural gas, nuclear..
In 2013, electrical energy souces in Turkey: %44 natural gas, %25 coil, %24 hydroelectric (water), %2
liquid fuel, %4 renewable.
In future, two nuclear power plant projects: Akkuyu and Sinop.
Electrical Energy generation:
Hydroelectric power plants, Thermal Power plants
Voltage Levels:
Low voltage < 1000V
High voltage > 1000V
1000V<Mid voltage<15000
Electric Distribution:
High voltage lines: 154kV, 380kV
High voltage lines:For the same power, High voltage,lower current, thiner wires.
Advantages of High voltage lines: Easy installation, Low cost conductors, low losses.
High voltage lines:
High voltage lines: 154kV, 380kV
Min height over highways: 14m
Max. Distance of approach: 2-3.5m
Isolators
Warning boals
Electrical System Installation Structures
Electrical Network: All the cables and air lines from the current supplier (transformer) to the consumer
devices.
Electrical Distribution Network: All the cables and air lines from the current supplier (transformer) to
the consumer facility.
Consumer facility: All the electrical systems after the main junction panel at the enterence.
Network System Types:
TT type networks contain a ground connection both at the generator and the consumer facility.
Consumer Facility Electrical Systems:
All electrical devices in workplaces are loads.
In electric sockets, there are two terminals: the + (phase) and the natural. For T type systems, there are
also ground contact points.
On-off switch for all electrical devices are connected to natural terminal. Otherwise the probability of
conducting the voltage to device’s chase is higher.
Electric shock:
It is the current flow over heart.
Usually, the current enters from hands, pass through heart, and leaves from feet.
The current passing through heart causes it to stop beating (fibrilation).
Fuses:
Fuses are safety devices against high currents.
Fuses operate as a switch controlled by current.
Fuses blow (open the switch) when the current exceeds certain limit.
Consumer Facility Electrical Systems:
The Ac cuurents comes from the positive (phase) terminal, pass through the load, and goes back to
generator from the natural line and eventually, goes to ground.
For any reason, if the phase terminal and natural terminal get contact, infinite current demand occurs,
this is called short circuit.
Fuses cut off the circuit when the cuurent exceeds certain limit thereby protecting systems from high
current damage.
Grounding:
Connecting all non-active (not under voltage) parts of all electrical devices (generators, transformers,
motor cutters, seperators, poles, ect.) to ground through conductors.
Fuses:
Deformation of insulators around the wires in time.
Thus, the chase of the device may get contact with the wire at 220 volts.
The chase is connected to ground, and as a result, the high current blows the fuse by providing safety
against electric shock.
Technical Factors in Electric Shocks:
Type of the current (AC-DC)
Amount of voltage
Amount of current
Frequency
Time of exposure
Major Factors in Electrical Accidents:
Wheather the ground is dry or wet
Existence of some Insulating objects between the voltage source and victim.
Current direction and path of flow.
Body resistance
Wheather hands being dry or wet.
Causes of Electrical Accidents:
Due to isolation faults (23%)
Due to faulty contact of the voltage to device chase (26%)
Due to contact by the power lines. (20%)
Due to accidents on top of electric poles. (12%)
Effects of electric current on human body:
The amplitude limit for safety is considered to be 30mA.
The safety precautions:
Cutting off the voltage
Insulation, isolation
Grounding
Static Electric: