Lab 10: Ohm's Law and Resistance

Learning Objectives

  • Verify the relationship between voltage, current, and resistance for an ohmic conductor.
  • Construct a voltage-current graph and determine resistance from its slope.
  • Compare measured resistance with nominal or color-code resistance.
  • Practice safe use of power supplies, ammeters, voltmeters, and resistors.

This placeholder is prepared for a complete laboratory experiment on Ohm's Law. It can be completed with physical circuit components, a breadboard, multimeters, variable DC supply, or a circuit simulation when equipment is limited.

Ohm's Law

For an ohmic conductor at constant temperature, voltage is proportional to current.

V=IRV = IR

Variables

SymbolDescriptionUnit
VVpotential difference or voltageV
IIelectric currentA
RRresistanceΩ

Resistance from graph

The slope of a voltage-current graph gives resistance.

R=ΔVΔIR = \frac{\Delta V}{\Delta I}

Suggested Apparatus

ApparatusPurpose
DC power supply or batteryProvides circuit voltage.
ResistorTest component.
Ammeter or multimeterMeasures current in series.
Voltmeter or multimeterMeasures voltage in parallel.
Breadboard and connecting wiresBuilds the circuit safely.
SwitchControls circuit operation.

Placeholder procedure outline

  1. Build a simple series circuit with the resistor and ammeter.
  2. Connect the voltmeter in parallel with the resistor.
  3. Start at a low voltage and record the corresponding current.
  4. Increase voltage in small steps and record voltage-current pairs.
  5. Avoid overheating the resistor by using safe voltage limits.
  6. Plot VV versus II and determine the slope.
  7. Compare the experimental resistance with the nominal value.

Data Table Placeholder

TrialVoltage, VCurrent, AComputed resistance, ΩRemarks
1
2
3
4
5

Electrical safety

Use low-voltage DC sources only for this introductory activity. Turn off the power before changing connections and do not short-circuit the supply.

To complete this lab

Add circuit diagrams, resistor color-code instructions, graphing requirements, sample calculation, and post-lab questions on non-ohmic behavior and temperature effects.

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