Electrical Math
Electrical Math
Ohm’s Law-1
What value of series resistor would be needed to obtain a full scale deflection on a 50 microamp DC meter with an applied voltage of 200 volts DC?
What value of series resistor would be needed to obtain a full scale deflection on a 50 microamp DC meter with an applied voltage of 200 volts DC?
4 megohms.
From wp2ahg:
Ohm's Law:
\[R=\frac{E}{I}\]
\[Ohms=\frac{Volts}{Amps}\]
\[R=\frac{200\text{ Volts}}{50\text{ Microamps}}\]
\[\frac{200\text{ Volts}}{0.00005\text{ Amperes}} = 4,000,000\text{ Ohms}\]
To convert into megaohms:
1 M = 10 ^{6} or 1,000,000
\[\frac{4,000,000\text{ Ohms}}{1,000,000\text{ mega}} = 4\text{ Megaohms}\]
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Which of the following Ohms Law formulas is incorrect?
Which of the following Ohms Law formulas is incorrect?
I = R / E
From crzy_ray:
V = voltage is Electromotive force or E
I = current in Amps
R = resistance in Ohms
\[{\text{I}=\frac{\text{R}}{E}}\]
Thus, the current equals resistance divided by volts or electromotive force.
For more information, please see Fluke site for the well-illustrated article What is Ohm’s Law?
When you see Ohm's law incorrect, it should raise your "IRE"
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If a current of 2 amperes flows through a 50-ohm resistor, what is the voltage across the resistor?
If a current of 2 amperes flows through a 50-ohm resistor, what is the voltage across the resistor?
100 volts.
From wp2ahg:
Ohm's Law:
\[E = I ∗ R\]
\[Volts = Amps ∗ Ohms\]
\[E = (2\text{ amps}) ∗ (50\text{ ohms}) = 100\text{ volts}\]
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If a 100-ohm resistor is connected across 200 volts, what is the current through the resistor?
If a 100-ohm resistor is connected across 200 volts, what is the current through the resistor?
2 amperes.
From wp2ahg:
Ohm's Law:
\[R=\frac{E}{I}\]
\[Ohms=\frac{Volts}{Amps}\]
\[\frac{200\text{ Amps}}{100\text{ Ohms}} = 2\text{ Amps}\]
V = voltage is Electromotive force or E
I = current in Amps
R = resistance in Ohms
\[{\text{I}=\frac{\text{R}}{E}}\]
thus, Current equals resistance divided by volts or electromotive force.
For more information, please see Fluke site for the well-illustrated article What is Ohm’s Law?
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If a current of 3 amperes flows through a resistor connected to 90 volts, what is the resistance?
If a current of 3 amperes flows through a resistor connected to 90 volts, what is the resistance?
30 ohms.
From wp2ahg:
Ohm's Law:
\[R=\frac{E}{I}\]
\[Ohms=\frac{Volts}{Amps}\]
\[\frac{90\text{ Volts}}{3\text{ Amperes}} = 30\text{ Ohms}\]
V = voltage is Electromotive force or E
I = current in Amps
R = resistance in Ohms
\[{\text{R}=\frac{\text{E}}{I}}\]
thus, resistance equals volts divided by amperes or electromotive force.
For more information, please see Fluke site for the well-illustrated article What is Ohm’s Law?
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A relay coil has 500 ohms resistance, and operates on 125 mA. What value of resistance should be connected in series with it to operate from 110 V DC?
A relay coil has 500 ohms resistance, and operates on 125 mA.
What value of resistance should be connected in series with it to operate from 110 V DC?
380 ohms.
From wp2ahg:
Ohm's Law:
\[R=\frac{E}{I}\]
\[Ohms=\frac{Volts}{Amps}\]
Mili (m) is 10^{-3} or 1/1,000
thus, 125 mA is 0.125 A
\[\frac{110\text{ Volts}}{0.125\text{ Amperes}} = 880\text{ Ohms}\]
Since the relay coil has 500 Ohms contributing to the circuit, then \[880\text{ Ohms} - 500\text{ Ohms} = 380\text{ Ohms}\]
V = voltage is Electromotive force or E
I = current in Amps
R = resistance in Ohms
\[{\text{R}=\frac{\text{E}}{I}}\]
thus, resistance equals volts divided by amperes or electromotive force.
For more information, please see Fluke site for the well-illustrated article What is Ohm’s Law?
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