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CSEEL (Center for Scientific Exploration and Experiential Learning) is a premier Indian STEM educational initiative offering hands-on science experiments, 3D live laboratory simulations, curriculum-aligned project kits, teacher training workshops, and national science conclaves aligned with NEP 2020.

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CSEEL shifts education from rote memorization to active inquiry and hands-on experimentation. Students observe, build, analyze, and apply scientific concepts to real-world challenges, developing critical thinking and scientific temper as envisioned by NEP 2020.

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Verification of Ohm's Law and Resistance Determination

Experiment video

What you will learn

Determine the resistance per unit length of a given wire by plotting a graph between potential difference (V) and current (I), verifying Ohm's Law (V = IR) at constant temperature.

Materials needed

Unknown Resistance Wire (Nichrome / Constantan) m
Unknown Resistance Wire (Nichrome / Constantan) m
₹50
What is it?
High-resistivity alloy wire (80% Ni, 20% Cr) with minimal temperature coefficient of resistance.
Specifications
Length
1.0 meter
Diameter
0.37 mm (28 SWG)
Resistivity
1.10 × 10⁻⁶ Ω·m
Mounting
Tensioned on wooden meter board
DC Voltmeter (0-3V range, least count 0.05V)
DC Voltmeter (0-3V range, least count 0.05V)
₹95
What is it?
Moving-coil DC voltmeter calibrated for accurate potential drop measurement.
Specifications
Range
0 – 3.0 V
Least Count
0.05 V (50 mV)
Internal Resistance
> 2000 Ω
Zero Adjuster
Mechanical screw on dial
DC Ammeter (0-1.5A range, least count 0.02A)
DC Ammeter (0-1.5A range, least count 0.02A)
₹140
What is it?
Dead-beat moving coil DC ammeter with clear mirror scale to eliminate parallax error.
Specifications
Range
0 – 1.5 A
Least Count
0.02 A (20 mA)
Internal Resistance
< 0.05 Ω
Damping
Eddy current air-damped
Rheostat (100Ω variable resistor)
Rheostat (100Ω variable resistor)
₹185
What is it?
Heavy-duty wire-wound variable resistor for smooth current regulation.
Specifications
Resistance
100 Ω
Current Capacity
1.5 A continuous
Core
Vitreous enameled porcelain tube
Slider
Phosphor bronze spring contact
DC Battery Eliminator / 2V Accumulator
DC Battery Eliminator / 2V Accumulator
₹230
What is it?
Regulated solid-state DC voltage source replacing lead-acid accumulators.
Specifications
Output Voltages
2V, 4V, 6V selectable DC
Current Rating
2.0 A max
Ripple
< 0.5% RMS
Protection
Inbuilt thermal fuse
One-way Plug Key with plug
One-way Plug Key with plug
₹275
What is it?
Solid brass contact block with removable tapered brass plug for positive circuit interruption.
Specifications
Block Material
Machined brass block
Base
Bakelite insulated pad
Resistance
< 0.002 Ω plugged
Plug
Knurled ebonite handle
Connecting Copper Wires & Sandpaper set
Connecting Copper Wires & Sandpaper set
₹320
What is it?
Heavy-gauge insulated copper connecting leads and abrasive sandpaper.
Specifications
Conductor
99.9% pure annealed copper
Gauge
18 SWG
Sandpaper
P220 aluminum oxide grit
Insulation
Double PVC sheath

Tick items as you collect them. Tap + to see the product, specifications and buy options.

Stay safe

Ensure all circuit connections are tight and clean.
Never keep the key plugged continuously; remove the plug between readings to prevent wire heating.
Voltmeter must always be connected in parallel and ammeter in series.
Check that zero errors of both meters are accounted for before taking readings.

Steps

0 of 7 steps done

1Clean the ends of all connecting wires with sandpaper to remove oxide insulation.
Observation
Clean shiny copper terminals guarantee near-zero contact resistance at all binding posts.
Safety
Use fine-grit sandpaper gently to avoid thinning the delicate copper leads.
2Assemble the circuit in series: battery positive to ammeter positive, ammeter negative to resistance wire, wire to rheostat, rheostat to key, and key to battery negative.
Observation
Polarities match correctly: Ammeter (+) connects directly to battery (+) eliminator.
Safety
Keep battery eliminator switched OFF while completing circuit wiring.
3Connect the voltmeter in parallel across the resistance wire observing correct polarity (+ to +, - to -).
Observation
Voltmeter is placed strictly across the test wire, drawing negligible branch current.
Safety
Ensure voltmeter terminals do not short-circuit across adjacent bare leads.
4Insert the plug key and slide the rheostat contact to achieve a low measurable current on the ammeter.
Observation
Ammeter needle deflects smoothly without fluctuating or sticking on the dial.
Safety
Never force the rheostat slider beyond its stop collar.
5Record the ammeter reading (I) and corresponding voltmeter reading (V).
Observation
At 0.10 A current, potential difference across the 1m wire reads exactly 0.50 V.
Safety
Unplug key immediately after reading to avoid Joule heating (I²Rt).
6Shift the rheostat slider to 5 distinct positions to record 5 sets of (V, I) readings.
Observation
Equal stepwise increments of 0.10 A generate uniform 0.50 V increments.
Safety
If wire feels warm to touch, wait 2 minutes before the next reading.
7Calculate resistance R = V / I for each trial and plot the V versus I graph on millimeter graph paper.
Observation
Calculated ratios V/I remain strictly identical at 5.00 Ω within ±1% experimental limit.
Safety
Switch off main power before dismantling circuit components.

Tap + on a step to see what you will observe and any safety tips.

Record your observations

Trial	Ammeter (I, Amperes)	Voltmeter (V, Volts)	Calculated R = V/I (Ω)
1	0.10 A	0.50 V	5.00 Ω
2	0.20 A	1.00 V	5.00 Ω
3	0.30 A	1.50 V	5.00 Ω
4	0.40 A	2.00 V	5.00 Ω
5	0.50 A	2.50 V	5.00 Ω

Tap a highlighted cell to write your own observation.

Result and conclusion

The V-I graph is a straight line passing through the origin. The constant slope (ΔV/ΔI) verifies Ohm's Law and yields the resistance of the unknown conductor.

R = V / I = 5.00 Ω (Constant slope of V-I graph)

Observation	What it means
Linear V-I Relation	Potential difference across the conductor is strictly directly proportional to current passing through it.
Constant Slope (ΔV/ΔI)	The resistance of the nichrome wire remains constant at 5.00 Ω across all applied voltages.
Ohmic Behavior Verified	Because temperature was held constant by disconnecting between trials, Ohm's law is verified.
Zero Offset Check	The line passes cleanly through the origin (0, 0), indicating zero voltmeter and ammeter offset errors.

Potential Difference (V) vs Current (I) Characteristic

Sample readings. Replace with your own results.

Experiment photos

Before the experimentDuring the experimentResult