DC basics · 3 min read
Ohms Law Current: the method, worked through
Ohm's law predicts current through an ideal linear resistor at a given voltage.
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Ohms Law Current
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DC basics01
Ohms Law Current
Ohm's law predicts current through an ideal linear resistor at a given voltage.
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Ohms Law Voltage
The voltage drop across a linear resistor follows the product of current and resistance.
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Ohms Law Resistance
A voltage-current pair determines the effective resistance of an ohmic component.
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DC Electrical Power
DC power is the rate of electrical energy transfer at a fixed voltage and current.
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Resistor Power from Current
Resistive heating grows with the square of current.
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Resistor Power from Voltage
A resistor exposed to a fixed voltage dissipates power inversely proportional to its resistance.
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Series Resistance
Resistors in a single current path add directly.
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Parallel Resistance
Parallel resistors share the same voltage and add their conductances.
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Three Parallel Resistors
Three parallel branches contribute conductance to a shared pair of nodes.
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Voltage Divider
An unloaded two-resistor divider sets a fraction of the input voltage at its midpoint.
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Divider Lower Resistor
Rearranging the divider relation finds the lower resistor for a target unloaded voltage.
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LED Series Resistor
A series resistor drops the supply voltage remaining after an LED's forward drop.
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LED Resistor Dissipation
The resistor dissipates the voltage it drops multiplied by the LED current.
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Resistance Tolerance Span
Tolerance describes the permitted deviation from a nominal resistor value.
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Capacitors in Parallel
Parallel capacitors share a voltage while their stored charges add.
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Capacitors in Series
Ideal series capacitors carry equal charge, giving reciprocal addition of capacitance.
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Capacitor Charge
Capacitance relates stored charge to voltage across the capacitor.
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Capacitor Stored Energy
Energy stored in an ideal capacitor grows with the square of voltage.
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RC Time Constant
The RC time constant sets the speed of a first-order charging or discharging response.
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RC Charging Voltage
A capacitor initially at zero volts approaches a fixed supply exponentially through a resistor.
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RC Discharging Voltage
An initially charged capacitor loses voltage exponentially through an ideal resistance.
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RC Low-Pass Cutoff
A first-order RC low-pass cutoff is the frequency where amplitude falls to one over the square root of two.
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Capacitive Reactance
An ideal capacitor's reactance magnitude decreases as frequency rises.
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Inductive Reactance
An ideal inductor's reactance magnitude increases with frequency.
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Inductor Stored Energy
An ideal inductor stores energy in its magnetic field.
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Series Inductance
Uncoupled series inductors add their inductances.
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Parallel Inductance
Uncoupled ideal parallel inductors combine by reciprocal addition.
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RL Time Constant
An RL time constant sets the exponential current response in a first-order circuit.
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LC Resonant Frequency
An ideal LC pair exchanges energy between electric and magnetic storage at its natural resonance.
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Series RLC Impedance
The impedance magnitude combines resistive and net reactive parts at a specified frequency.
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Sine RMS Voltage
A sinusoid's RMS voltage produces the same resistor heating as the equivalent DC voltage.
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Sine Peak Voltage
A sine-wave peak is the RMS level multiplied by the square root of two.
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AC Apparent Power
Apparent power is the product of RMS voltage and current.
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AC Real Power
Real power uses power factor to account for the relationship between voltage and current.
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Power Factor
Power factor compares real power with the RMS-based apparent power.
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Battery Nominal Energy
Nominal battery energy combines a rated voltage with charge capacity.
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Ideal Battery Runtime
A constant-power load consumes stored usable energy at a steady rate in the ideal model.
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Battery Capacity Conversion
Converting milliampere-hours to watt-hours makes capacities at different voltages comparable.
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Ideal Charge Time
A constant-current charge model estimates the time to transfer a specified amount of charge.
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Current Divider Branch
In two parallel resistive branches, more current takes the lower resistance path.
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Non-Inverting Amplifier Gain
An ideal non-inverting op-amp circuit sets gain through its feedback ratio.
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Inverting Amplifier Gain
An ideal inverting amplifier reverses signal polarity and scales its magnitude by a resistor ratio.
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Voltage Gain in Decibels
An amplitude ratio maps to decibels with a factor of twenty.
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Power Gain in Decibels
Decibels express power ratios on a logarithmic scale.
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Decibels to Voltage Ratio
Exponentiation reverses an amplitude-gain decibel value.
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Frequency to Period
Period and frequency are reciprocal measures of repetition.
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PWM Duty Cycle
Duty cycle expresses the fraction of a repeating period spent high.
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PWM Average Voltage
A zero-low-level PWM signal has an arithmetic mean set by its high level and duty fraction.
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ADC Ideal Step Size
An ideal ADC divides a reference span into equally spaced quantization intervals.
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ADC Ideal Code
An ideal unipolar ADC maps the input into a quantization bin.
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