OHM

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OHMs LAW

• One microampere flowing in one ohm causes a one
  microvolt potential drop

Georg Simon Ohm
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How voltage, current, and resistance relate
Quantity Symbol Units Unit Abbreviation
Current I Ampere (Amp) A
Voltage E or V Volt V
Resistance R Ohm ?
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Ohms Law

• EIR V
• IE/R A
• RE/I ?

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Triangle Relations
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Example

• RE/I
• R36/412 Ohm

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An Analogy for Ohms Law

• Pressure (P) Voltage (V)
• Flow (Q) Current (A)
• Resistance (?) Resistance (?)
• PQR VIR

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Torque, Work, and Power

• Torque is the amount of twisting force produced
  by the engine (NM)
• Mechanical Work is the lifting of a weight
  against the pull of gravity
• Electrical Work is the lifting of charges
  against the resistance (Jules)
• Mechanical Power is the rate of change of work
  done to lift the weight
• Electrical Work is the rate of change of work
  done to lift the charges (VA)

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Torque, Work, and Power

• Torque is the amount of twisting force produced
  by the engine (NM)
• Work is the lifting of an object against a
  resistance (Jules)
• Power is the rate of change of work done to lift
  an object

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Mechanical Power HorsePower (hp)

• Hp 476 watt
• 100 hp diesel tractor engine is slower than 100
  hp electrical engine, however, the former provide
  more amounts of torque than the latter.

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Ohms law for calculating power

• PIE (1)
• EIR (2)
• From (1) and (2), the following formula can be
  written

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Example

• Calculate the power in the circuit shown in fig.
• IE/R12 A
• PIE1236
• 432 watt or
• 432/746 hp

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Resistors
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(No Transcript)
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Resistors are rated in terms of how much they can
dissipate without overheating and sustaining
damage (025 watt or less)
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Nonlinear conditions and negative resistance
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Circuit Wiring
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Polarity of Voltage Drop
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Summary

• Ohms Law
• Voltage and Pressure
• Current and Flow
• Resistance
• Ohms power law
• Circuit wiring and the polarity of voltage drop