Electrical Measurement, Ohm’s Law, & Watt’s Law CVSD Electronics 1.

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Transcript of Electrical Measurement, Ohm’s Law, & Watt’s Law CVSD Electronics 1.
Electrical Measurement, Ohm’s Law, & Watt’s Law
CVSDElectronics 1
Resistance A measure of the opposition to the flow
of electrons (current) through a material
Unit of Measurement: Ohm (Ω)
Symbol: R = Resistance
Current A measure of the total amount of
electrons flowing in a circuit in a given unit of time
Unit of Measurement: Ampere (A)
Symbol: I = Intensity
Voltage A measure of the Electromotive Force
(EMF) or pressure that pushes electrons through a circuit
Unit of Measurement: Volt (V)
Symbol: E = Electromotive Force
Power A measurement of the rate of consuming
energy, transferring energy, or doing work
Unit of Measurement: Watt (W)
Symbol: P
Ohm’s Law Describes the mathematical relationship
between resistance, current, and voltage
Voltage (E) = Amperage (I) x Resistance (R)
With two of these values, you can use Ohm’s Law to find the third
Variations of Ohm’s Law E = IxR I = E/R R = E/I
Ohm’s Law Example E = 24 VDC I = ? R = 12 Ω
E=IR
24=Ix12
I = 24/12
I = 2 A
Calculations
Watt’s Law Describes the mathematical relationship
between power, current, and voltage
Power (P) = Amperage (I) x Voltage (E)
With two of these values, you can use Watt’s Law to find the third
Variations of Watt’s Law P = IE I = P/E E = P/I
Watt’s Law Example P = 36 W I = ? E = 12 V
P=IE
36=Ix12
I = 36/12
I = 3 W
Calculations
Combinations of Ohm’s and Watt’s Laws
Measuring Resistance with the DMM Must select Ohmmeter Range (Ω) Pos (+) lead must be in Volt/ Ohm pin Sat meter to proper range Must wire in parallel with circuit Power must be removed from the circuit
Measuring Voltage with the DMM
Must select DC Voltage Range Pos (+) lead must be in Volt/ Ohm pin Set meter to proper range Must wire in parallel with the circuit Circuit must be have power
Measuring Current with the DMM Must select DC Current Range Set meter to proper range. (meter can be
damaged if not set to the proper range) Must wire in series with the circuit Circuit must be have power
Measured Tolerance Predicted values, and measured
values may not always be exactly the same There is unaccounted for resistance in the
wires etc. Applied voltage may fluctuate Human error may disturb measurements Components have tolerance (not always
exact values) As components change temperature,
resistance may also change
Review State Ohm’s Law State Watt’s Law How is voltage measured? How is resistance measured? How is current Measured? Why do predicted and calculated
values differ?