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Ohms Law (Practical 2)
Sula Ntsaluba
Overview
This video provides a practical guide to verifying Ohm's Law, a fundamental principle in electrical circuits. It details the setup and execution of an experiment where voltage and current are measured across resistive components. The demonstration covers connecting multimeters as ammeters (in series) and voltmeters (in parallel), using breadboards for circuit assembly, and working with different resistor values (100 ohm and 10 kOhm). The experiment involves varying the input voltage from 5 to 30 volts and plotting the resulting voltage-current relationship. It also briefly touches upon using a potentiometer to achieve variable resistance and measuring resistance values directly. The core objective is to experimentally confirm the linear relationship between voltage and current in a resistive circuit as stated by Ohm's Law.
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Chapters
- •Practical 2 aims to verify Ohm's Law.
- •Ohm's Law states that voltage is proportional to current in a resistive element (V=IR).
- •This implies a linear relationship between voltage and current if resistance is constant.
- •The experiment involves measuring voltage and current across a resistor.
- •The circuit consists of a voltage source, a resistor, an ammeter, and a voltmeter.
- •Ammeters measure current and must be connected in series.
- •Voltmeters measure voltage across a component and must be connected in parallel.
- •The experiment requires ranging the input voltage from 5V to 30V.
- •Measurements will be taken for specific input voltages (5V, 10V, 15V, 20V, 25V, 30V).
- •For each voltage, the voltage across and current through the resistor are measured.
- •A graph of voltage versus current will be plotted.
- •The experiment is repeated with a low resistance value (e.g., 10 ohm or 100 ohm) and a high resistance value (e.g., 5-10 kOhm).
- •Essential equipment includes two multimeters (for voltmeter and ammeter functions), a breadboard, connection cables, resistors (100 ohm, 10 kOhm), and a power source (DC power supply or 9V battery for demonstration).
- •Breadboards have internal connections: vertical strips for component rows and horizontal strips for power rails.
- •Understanding these connections is crucial for assembling the circuit.
- •Connecting the power source to the breadboard's power rails.
- •Placing a resistor (e.g., 10 kOhm) onto the breadboard, ensuring its leads are in different connected rows.
- •Using a multimeter set to DC Volts to measure the voltage across the resistor to confirm connectivity and power supply function.
- •A diode can be added for visual indication of current flow (it lights up when forward-biased).
- •The diode is connected in series after the resistor.
- •Voltages across the resistor and the diode can be measured separately.
- •The sum of voltage drops across components should ideally equal the source voltage (Kirchhoff's Voltage Law).
- •The ammeter must be connected in series with the circuit.
- •To insert the ammeter, a connection point in the series path is broken, and the ammeter is placed across the break.
- •The multimeter must be set to the correct DC current range (e.g., milliamps) based on expected current values.
- •Measurements are taken with both low (100 ohm) and high (10 kOhm) value resistors to observe the change in current.
- •A potentiometer can be used as a variable resistor.
- •It has three terminals; two are used to create a variable resistance path.
- •The potentiometer can be connected in series with the circuit.
- •The resistance value can be adjusted by turning the potentiometer's knob, and measured directly using the multimeter set to Ohms.
Key Takeaways
- 1Ohm's Law (V=IR) describes the linear relationship between voltage, current, and resistance in a circuit.
- 2Ammeters must be connected in series to measure current, while voltmeters must be connected in parallel to measure voltage.
- 3Breadboards provide a convenient way to build and modify prototype circuits.
- 4Accurate measurement requires setting multimeters to the correct function (Volts, Amps, Ohms) and range.
- 5The experiment involves systematically varying voltage and measuring corresponding current to verify Ohm's Law.
- 6Using different resistor values (low vs. high) demonstrates how resistance affects current flow for a given voltage.
- 7A potentiometer allows for adjustable resistance, useful for experiments requiring variable resistance.
- 8Experimental results, when plotted as voltage vs. current, should yield a straight line for a purely resistive component, confirming linearity.