HUKUM JOULE – Praktikum Fisika Listrik Magnet | ITS Surabaya

Summary

In this video, Silvia Nur Aziza, a physics lab assistant at ITS, introduces a basic physics experiment focused on Joule’s Law. The experiment aims to determine the heat generated by electric current and verify the equivalence of Joule’s work in calories. Key concepts like the relationship between current, resistance, and heat, along with formulas like Q = I² * R * T and H = V * I * T, are explained. The procedure involves measuring temperature changes in water and calorimeters, and calculating heat transfer to determine the value of 1 Joule in calories. The video also includes data collection and analysis steps, highlighting error margins and experimental insights.

Takeaways

• 😀 The experiment demonstrates Joule's law, which relates the heat generated by electric current in a conductor to the current's square, resistance, and time.
• 😀 The formula for Joule's law is Q = I² * R * T, where Q is the heat energy (in joules), I is the electric current (in amperes), R is resistance (in ohms), and T is time (in seconds).
• 😀 Joule's law can also be expressed as Q = V * I * T, where V is voltage, I is current, and T is time.
• 😀 The experiment also uses the formula Q = MCΔT, where M is the mass of water in grams, C is the specific heat capacity of water (1 cal/g°C), and ΔT is the temperature change.
• 😀 The experiment requires two heat sources: the calorimeter itself and the water inside it, with Q1 being the heat received by the water and Q2 being the heat received by the calorimeter.
• 😀 According to the law of energy conservation, the heat provided by the electrical current (H) must be equal to the total heat received by the water and calorimeter (Q1 + Q2).
• 😀 To determine how many calories equal 1 joule, the formula H = Q1 + Q2 is used, and the heat is measured in calories while the electrical energy is in joules.
• 😀 Key experimental data include the mass of water (in grams), the electric current (amperes), and the temperature rise (from 30°C to 40°C).
• 😀 The experimental procedure involves recording data for various currents (2A, 3A, 4A) and noting the voltage and time taken for each 1°C temperature rise.
• 😀 After conducting the experiment, calculations are made to find the total heat generated by the current (H), the heat received by the water (Q1), and the heat absorbed by the calorimeter (Q2). The value of 1 joule is then determined in calories.
• 😀 The experiment concludes by comparing the experimental result for 1 joule (0.24 calories) with the theoretical value of 1 joule = 0.239 calories, yielding a percent error of 4.17%.

Q & A

What is the main objective of the experiment described in the transcript?

The main objectives are to determine the heat generated by electric current and to verify Joule's law by calculating the value of 1 Joule in calories.

What is Joule's law and how is it mathematically expressed?

Joule's law explains the relationship between the heat produced by electric current, the current itself, the resistance of the conductor, and the time during which the current flows. It is expressed as Q = I² * R * T, where Q is the heat energy in Joules, I is the current in amperes, R is the resistance in ohms, and T is the time in seconds.

How does the equation for heat change when using Ohm's law?

Using Ohm's law (V = I * R), the equation for heat can be rewritten as Q = V * I * T, which is another form of Joule's law.

What is the significance of using the formula Q = MCΔT in this experiment?

The formula Q = MCΔT is used to calculate the heat absorbed by water (Q1) and the calorimeter (Q2). It helps in determining the heat transfer and the energy balance in the experiment.

Why is it important to note that the mass of water is measured in grams rather than kilograms?

In this experiment, the mass of water is used in the formula Q = MCΔT, and since the specific heat of water is often given in calories per gram, it is important to use grams instead of kilograms to maintain consistency in units.

What equipment is used in the experiment?

The equipment includes a calorimeter, thermometer, stopwatch, balance scale, crocodile clips, power supply, and water.

How is the data collected during the experiment?

Data is collected by measuring the voltage, current, and the time required to raise the temperature of the water by 1°C in the calorimeter. The measurements are taken at various current values (2A, 3A, 4A), and the data is recorded for each variation.

What are the steps involved in the experiment methodology?

The steps involve setting up the apparatus with the thermometer and calorimeter, adding a specific mass of water, connecting the power supply, and measuring the time taken to increase the temperature of the water by 1°C. This is repeated for different current values and multiple trials.

How is the value of 1 Joule in calories determined from the experiment?

The value of 1 Joule is determined by equating the heat supplied by the electric current (in Joules) to the heat absorbed by the water and calorimeter (in calories). Using the formula H = Q1 + Q2, and applying the principle of conservation of energy, the result is obtained by converting between the units.

What was the calculated value of 1 Joule in calories, and how does it compare to the theoretical value?

The calculated value of 1 Joule was approximately 0.2461 calories, which was rounded to 0.25 calories. The theoretical value is 1 Joule = 0.24 calories. The experimental error was 4.17%, which shows a reasonable agreement between the experimental and theoretical values.