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Module-1Ohm’s law

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By the end of this lesson, the student will be able to: 1-Use prefixes to convert electrical quantities. 2-State Ohm's Law and define the relationship between current, voltage, and resistance.3-Use Ohm's Law to solve unknown quantitiesof current, resistance, or voltage.4-Apply the power formula to calculate the power in a circuit.

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1- Introduction to Ohm's Law.2-Investigations of Ohm's Law using Edison Version 4 simulator.3-Electrical Units and Prefixes. 4-Electrical Power.

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It states that the current passing through a conductor between two points is directly proportional to the potential difference (i.e. voltage drop or voltage) across the two points, and inversely proportional to the resistance between them, at a constant temperature.

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R

VI

Mathematical Equation is

Ohm's Law Formulas

Find CurrentFind VoltageFind Resistance

Current equals voltage divided by resistance

V= I x R

Voltage equals current multiplied by resistance

Resistance equals voltage divided by current

R

VI

I

VR

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Screen layout

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Circuit connection

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Voltage and current measurement

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Suppose a 10KΩ carbon resistor is connected to a 12V battery .Calculate the current flow.

I=V/R

I= 12/10000= 1.2 mA.

Suppose a solar cell provides a current of

2.5 mA to a 500 ohm load. Calculate the output voltage of the solar cell:

V= I X R

V= 2.5mA X 500 ohm

V= 1.25 V

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QuantityUnit of MeasureFunction

Name Symbol Name Symbol

Voltage UV

Emf

Volt VVoltage is the electromotive force or pressure which makes current flow in a circuit

Current IAmpereACurrent is the flow of electrons through a circuit

Resistance ROhm ΩResistance is the opposition to current flow offered by electric devices in a circuit

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Metric prefixes table

NumberPower of Ten Prefix Symbol

One billion1,000,000,000109gigaG

One million1,000,000106megaM

One thousand 1,000103kiloK

One 1100------

One thousandth 0.00110-3milliM

One million 0.00000110-6microμ

One billionth 0.00000000110-9nanon

One trillion 0.00000000000110-12picop

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Electrical power is defined as the potential energy or voltage times the current passing through the device.

P = VI

Where:

P = electrical power in Watt (W)

V = voltage used in Volt (V)

I = current in Amperes (A)

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Suppose an electric heater draws a current of 8A when connected to its rated voltage of 235V. The power rating of the heater is :

P = VI=235x8=1880W=1.88 KW

Suppose a current of 30A is being supplied to an electric load. The total resistance of the wire used to supply this current is 0.1 Ω. The power that lost in the wire is:

P = I2 x R = (30)2 X 0.1 = 90 W

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