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Presentation on theme: "Electricity."— Presentation transcript:

1 Electricity

2 The word electricity is used to describe a variety of phenomena resulting from the presence and flow of electric charge. Examples of electrical phenomenon include: electric shock, lightning, sparks In scientific work different terms are used to describe these related (but different) phenomena. Electric charge: physical property of matter which causes it to experience a force when near other electrically charged matter The common subatomic particle with a negative charge is the electron. The common subatomic particle with a positive charge is the proton.

3 Electrical charges are usually due to objects having gained or lost electrons.
Static Electricity is usually caused when dissimilar materials are rubbed together, transferring electrons from one to the other. This transfer of electrons results in the objects developing an electric charge. Electric charges on objects are either positive or negative. Objects with excess electrons have negative charges whereas objects which have lost electrons have positive charges. Objects with electric charges exert forces on other charged objects. Objects with the same electric charges (attract / repel) each other. Objects with different (opposite) electric charges (attract / repel) each other.

4 Electric charges are measured in Coulombs (C).
Electric Current is the flow of electric charge. Usually we are referring to the movement of electrons. Electrical current is measured in amperes commonly abbreviated amps which have the symbol A. Substances which allows the (easy) movement of electrons are called conductors. Substances which prevent the flow of electrical current are called insulators. There are no materials which perfectly prevent the flow of electrical current. Electrical resistance is measured in ohms which have the symbol Ω. Electric Voltage is the "push" behind electric current.

5 Ohm's Law is a mathematical equation which relates voltage,
Electrical potential is measured in voltage (volts) which have the symbol V. Ohm's Law is a mathematical equation which relates voltage, current, and resistance. Ohm's Law can be written: voltage = current x resistance Where: The Variable Represents Measured In V Voltage Volts I Current Amperes R Resistance Ohms

6 Solve these problems using Ohm's Law:
22. If a 6 V battery is connected to a light bulb whose resistance is 55,000 Ω how much current will flow in the circuit? 23.A certain electric heater is rated for 120 V and a current of 10 A. What must be the minimum resistance of the heating element? 24. If I wanted to make a 10A current flow through a 250 Ω resistor what voltage should I apply?

7 power = current x voltage
Electrical Power In science Electric Power is defined as the rate at which electrical energy changes from one form to another. Electrical power is measured in watts which have the symbol w. Electrical power is related to current and voltage by the equation:  power = current x voltage

8 Where: The Variable Represents Measured In P Power Watts I Current
Amperes V Voltage Volts

9 Try these problems related to electrical power:
29.How much current is used by a 25 W light bulb (120 V)? 30.A vacuum cleaner's motor is rated for 9 Amps and 120 V. What is the power of the motor in Watts? 31.Which consumes more power a 24 V motor at 9 A or a 120 V motor at 5 A?

10 Electric Circuits A(n) circuit is a path for electricity to flow through. A circuit is said to be closed if electricity can flow through it and open if electricity can not flow. Series circuits which allow only one path for electricity to follow. Parallel circuits which allow multiple paths for electricity to follow.

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