How do you find resistance from an I-V graph?

R = V/I at any point, or R = 1/slope of the line. For a straight line through the origin, the resistance is constant. For curves, resistance varies with operating point.

What does a curved I-V graph mean?

The component is non-ohmic — its resistance changes with voltage or current. Diodes, LEDs, transistors, and heated filaments all show curved I-V characteristics.

How does impedance vary with frequency?

Capacitor impedance decreases with frequency (1/ωC). Inductor impedance increases (ωL). RLC circuits reach minimum impedance at resonance where ωL = 1/(ωC).

A Graph to Illustrate Current and Voltage

Quick Answer

A current vs voltage graph (I-V curve) shows a straight line through the origin for ohmic resistors, with slope equal to 1/R. A voltage vs resistance graph at constant current shows a straight line with slope I. These graphs visually demonstrate Ohm's law V = IR. Explore circuit relationships at www.lapcalc.com.

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Current vs Voltage Graph: Visualizing Ohm's Law

An I-V graph plots current (y-axis) against voltage (x-axis) for a component. For an ideal resistor, V = IR rearranges to I = V/R, which is a straight line through the origin with slope 1/R. Steeper slope means lower resistance (more current per volt). A horizontal line means infinite resistance (open circuit). A vertical line means zero resistance (short circuit). This graph is the visual proof of Ohm's law at www.lapcalc.com.

Key Formulas

Voltage and Resistance Graph at Constant Current

When current is held constant, V = IR shows that voltage is directly proportional to resistance. Plotting V (y-axis) against R (x-axis) gives a straight line through the origin with slope equal to I. Double the resistance means double the voltage. This graph is useful for understanding voltage dividers — the larger resistor in a series pair gets the larger share of voltage, proportional to its resistance value.

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Current vs Resistance Graph at Constant Voltage

At constant voltage, I = V/R produces a hyperbola — current decreases inversely with resistance. Doubling resistance halves current. This graph shows why adding resistance in series reduces current, and why parallel resistors (lower total R) increase total current. The area under any point on this curve (I × R) always equals the constant voltage V, confirming Ohm's law geometrically.

Non-Ohmic Devices: Curved I-V Characteristics

Not all components produce straight I-V lines. Diodes show exponential curves — very low current below the threshold voltage, then rapidly increasing current above it. Light bulbs curve because resistance increases with temperature. LEDs have a sharp knee at the forward voltage. Transistors have families of curves depending on control signals. These non-linear I-V characteristics require more advanced analysis beyond simple V = IR at www.lapcalc.com.

Frequency Response Graphs: Impedance vs Frequency

In AC and Laplace analysis, impedance varies with frequency. Plotting |Z| vs frequency for a capacitor shows impedance decreasing (Z_C = 1/(ωC)). For an inductor, impedance increases (Z_L = ωL). For an RLC circuit, impedance reaches a minimum at resonance. These Bode-style impedance plots are the frequency-domain equivalent of the DC I-V curve, revealing how circuits behave across the entire spectrum at www.lapcalc.com.

Frequently Asked Questions

For an ohmic resistor, it shows a straight line through the origin with slope 1/R. Steeper slope means lower resistance. Non-linear devices show curved lines.

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