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Simple circuit Components: Power Source Conductor Resistor 4

Simple circuit Components: Power Source Conductor Resistor 4

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Simple circuit Components: Power Source Conductor Resistor Circuit diagram: 4

Simple circuit Components: Power Source Conductor Resistor Circuit diagram: 4

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Exploring a Simple Circuit Components: Power Source Conductor Resistor 4

Power

Power Cell : A basic unit capable of producing an electromotive force. Emf is the force that causes electrons to move in a conductor.

How Cells work

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How Cells work

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There are electrons/charges in every conductor There are electrons/charges in every conductor. Charges/electrons gain Energy as they pass through a power supply and lose energy as they pass through a resistor (an electric appliance that consumes electricity). The energy difference (potential difference) is measured in volts and it’s called Voltage (the potential difference between any two parts of a circuit, see page 2.20). The voltage in a circuit is measured using a voltmeter connected parallel to the circuit. (See page 2.19 and explore the potential difference between different parts of the circuit).

Power Supply

Charge Charge(Q, measured in Coulombs or ampere-hours) is a fundamental property of matter. It can be positive, negative or neutral. Electricity is energy based on the movement of negatively charged particles of which the smallest is an electron. An electron has one negative charge. The charge of one electron is so small that charge is measured in bulks of electrons. The SI unit for charge is Coulombs. The charges of 6.25 X 1018 electrons is equal to one Coulomb. Thus 6.25 X 1018 electron charge = 1 Coulomb 1 electron charge = 1.6 X 10-19 Coulomb Although it takes many electrons to produce one unit of charge, several units of charge can pass through a conductor or cell per second.

Current Current (I, measured in Amperes) is the rate of electron flow through a circuit or the number of charges crossing a particular part in a conductor in a given second. The direction of current is conventionally accepted to be from the positive terminal to the negative terminal of the power supply although electron-flow is opposite to that direction. Current is represented by the letter I and it is measure using an Ammeter which is connected in series with the circuit .

Current Current (I, measured in Amperes) is the rate of electron flow through a circuit or the number of charges crossing a particular part in a conductor in a given second. Current(I) = number of charges(Q) = number of coulombs(C) Time(t) seconds(s)

A charge of 5×10-6 Coulombs passes a given point in a wire every 2 seconds. What is the current in the wire?

A current of 5 mA (1 mA = 0. 001 A) flows in a circuit A current of 5 mA (1 mA = 0.001 A) flows in a circuit. Over a period of one hour, how much charge passes a given point in the circuit?

An electric kettle operates for 15 minutes An electric kettle operates for 15 minutes. Determine the charge that flow in the circuit is that period of time. In Coulombs 2. In Ampere-hour(Ah)

How long will it take a color television to consume 9 How long will it take a color television to consume 9.25×106 Coulombs of charges?

Calculate the charge produced by a car battery when starting the car if the battery draws a 130-A current for five minutes. Give your answer in ampere-hours.

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Resistance and Types of Materials Conductors are materials that contain moveable electrical charges; conduct electricity. Most conductors are metallic, silver is the best conductor(Al, Cu, Ag, Fe…). Some non metallic conductors are salt solutions, plasma and graphite

Resistance and Types of Materials Insulators are materials that resist or retard electron flow; do not conduct electricity. They are mostly not metals like plastic, rubber, air, porcelain, glass, mica (aluminum silicate)

Resistance and Types of Materials Semi-Conductors are materials that allow electrical conductivity greater than insulators but less than conductors. Examples are gallium, germanium and silicon are the most common and they are mostly used for transistors(switches or amplifiers in circuits), diodes (ultra-fast switches in circuits), in solar cells and computer memories.

Resistance Any material that allows current to run through it has resistivity (resistance to flow). Good Conductors have very little resistance or negligible amount. Resistive conductors have high resistance (Tungsten, Iron, Nichrome, Carbon). These are materials that conduct electricity less efficient than conductors but better than semi-conductors.

Resistance is the number of volts required for 1A of current to flow in a conductor; thus the ratio between the voltage and the current. This relationship, Ohms law, is valid when temperature is constant and it is expressed mathematically as V = I R or R = V/I

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Silver Quartz 68

ε ρ Volt V Volt V Ohm Ω R Volt V Ampere A I Ohm-meter Ω-m Coulomb –or- amp-hour C or A-h Q 71

End of Chapter