Electricity Basics

Definitions

• Ohm's Law is a fundamental principle in electricity that relates voltage, current, and resistance.

• Ohm's Law can be mathematically expressed as V = I × R, where V is voltage, I is current, and R is resistance.

• Ohm's Law can be applied in a circuit to calculate voltage, current, or resistance if the other two values are known.

• Electrical power is the rate at which electric energy is transferred or converted.

• The formula for calculating electrical power is P = V × I, where P is power, V is voltage, and I is current.

• Power is related to voltage and current, as it depends on the product of voltage and current.

• Potential difference is the difference in electric potential between two points in a circuit.

• Potential difference is measured in volts (V) and is often denoted by the symbol ΔV.

• Potential difference is important in a circuit as it drives the flow of electric current.

• Electric current is the flow of electrons through a conductor.

• The unit of electric current is the ampere (A).

• Current flows in a conductor due to the movement of charged particles, such as electrons.

Equations

• Ohm's Law equation is V = I × R, relating voltage, current, and resistance.

• If a device has a voltage of 12V and a current of 2A, the resistance can be calculated using Ohm's Law: R = V / I = 12V / 2A = 6Ω.

• The equation for electrical power is P = V × I, where P is power, V is voltage, and I is current.

• If a device has a potential difference of 10V and a current of 3A, the power consumption can be calculated as P = V × I = 10V × 3A = 30W.

• The equation relating potential difference, current, and resistance is V = I × R.

• Given a potential difference of 9V and a resistance of 3Ω, the current can be calculated as I = V / R = 9V / 3Ω = 3A.

• Current can be calculated using the equation I = Q / t, where I is current, Q is charge, and t is time.

• If a circuit has a charge of 15C passing through it in 5 seconds, the current can be calculated as I = Q / t = 15C / 5s = 3A.

Practical Experiments

• The setup for an experiment to investigate the current-voltage characteristics of a filament lamp involves connecting a filament lamp to a power source and varying the voltage while measuring the current.

• The graph of current against voltage for a filament lamp is expected to be non-linear, with current increasing rapidly at low voltages and slowing down at higher voltages.

• The resistance of a filament lamp changes as the voltage increases, with the lamp becoming less resistive at higher voltages.

• The setup for an experiment to measure the current-voltage characteristics of a diode involves connecting a diode to a power source and varying the voltage while measuring the current.

• The expected shape of the I-V graph for a diode is non-linear, with the current increasing rapidly at a certain voltage (the threshold voltage) and then increasing more slowly.

• The concept of forward and reverse bias in a diode refers to the direction of the voltage applied to the diode, with forward bias allowing current to flow and reverse bias blocking current.

• The procedure to determine the current-voltage characteristics of an ohmic resistor involves connecting the resistor to a power source and varying the voltage while measuring the current.

• The expected relationship between current and voltage for an ohmic resistor is linear, with current directly proportional to voltage.

• The resistance of an ohmic resistor behaves with changes in temperature, increasing as the temperature increases.

• The experiment to measure the resistance of a length of wire involves connecting the wire to a power source and varying the length of the wire while measuring the resistance.

• The length of the wire affects its resistance, with longer wires having higher resistance.

• If the resistance of a wire is directly proportional to its length, doubling the length of the wire will double its resistance.

Application and Analysis

• Given a circuit with a 24V battery and a resistor of 12Ω, the current flowing through the circuit can be calculated using Ohm's Law: I = V / R = 24V / 12Ω = 2A.

• If the resistance in the circuit is increased to 24Ω, the new current can be calculated as I = V / R = 24V / 24Ω = 1A.

• The power consumption of a device operating at 120V and drawing a current of 2A can be calculated as P = V × I = 120V × 2A = 240W.

• If the power consumption of a device is 150W and it operates at a current of 5A, the voltage across the device can be calculated as V = P / I = 150W / 5A = 30V.

• From an I-V graph of a diode, the threshold voltage can be determined by finding the voltage at which the current begins to increase rapidly.

• The I-V characteristics of a filament lamp differ from that of an ohmic resistor in that the lamp has a non-linear relationship between current and voltage, while the resistor has a linear relationship.