Electric Circuits Lesson-5 PDF

Electric Current - The flow of electric charge through a conductor, typically measured in amperes (A). Conventional Current: The flow of positive charge from the positive terminal to the negative terminal of a power source, used for historical reasons.  Electron...

Electric Current - The flow of electric charge through a conductor, typically measured in amperes (A). Conventional Current: The flow of positive charge from the positive terminal to the negative terminal of a power source, used for historical reasons.  Electron Flow: The actual flow of negatively charged electrons from the negative terminal to the positive terminal of a power source. Resistance: The opposition to the flow of electric current in a material, measured in ohms. Resistivity: A property of a material that determines its resistance to current, dependent on the material's nature, temperature, and dimensions. Conductivity: A material's ability to conduct electric current, the inverse of resistivity, often measured in siemens per meter (S/m). Ohmic Materials: Materials that have constant resistance regardless of the current and voltage Non-Ohmic Materials: Materials whose resistance changes with voltage or current Electromotive force - The energy supplied by a source per unit charge, typically measured in volts.  Potential Difference (PD): The difference in electric potential between two points in a circuit, which causes the current to flow.  Power: The rate at which electrical energy is transferred or converted, calculated as P = VI, measured in watts (W). Ohm's Law: The relationship between voltage (V), current (1), and resistance (R), expressed as V = IR.  Describe how electric work. Describe how temperature affects the resistance of metallic conductors. Differentiate between ohmic and non-ohmic materials using their I-V curves. Explain how wire dimensions (length and cross-sectional area) affect resistance. Solve current, resistance, and resistivity in contexts such as batteries, fuses, and household wiring safety.  The flow of electric charge through a conductor, such as a wire, due to the presence of an electric potential difference (voltage). It is essentially the movement of charged particles, typically  The amount of charger passing through any point in a conductor IN SYMBOLS: per unit time. 1 A = 1 C/s Q - Charge in coulombs t - time in seconds  Conventional current is the flow of positive charge from the positive terminal of a power source (higher potential) to the negative terminal (lower  Electron current refers to the actual flow of negatively charged electrons in a conductor. Electron flow is opposite to the direction of conventional current.  DC is a type of electric current where the flow of electric charge is unidirectional, meaning it moves consistently in one direction. CHARACTERISTIC: The voltage (potential difference) across the circuit remains constant. The current does not change direction over time. Example: Batteries Solar cells DC power supplies Application: Low-voltage devices like flashlights, calculators, and portable electronics. Used in electric vehicles and renewable energy systems.  AC is a type of electric current where the flow of electric charge periodically reverses CHARACTERISTIC: direction. The voltage alternates between positive and negative values in a sinusoidal or other repeating waveform. The current changes direction at Example: Power plants Wall outlets in homes and buildings Application: Used for transmitting electricity over long distances (e.g., power grids). Powers household appliances, lights, and industrial machines.  A measure of a material's opposition to the flow of electric current. It determines how much a material or circuit element restricts the movement of electric charges when a voltage is applied. The SI unit of resistance is the Ohm (Ω), where:  Provided by resistors with a constant value of resistance Carbon Resistor Metallized Film Resistor Wire-wound Resistor  Resistance can be adjusted Potentiometers Rheostat  Most resistors have 4, 5, or 6 color bands, with each band having a specific 1. First Band: purpose: Represents the first digit of the resistance value. 2.Second Band: Represents the second digit of the resistance value. 3. Third Band (Multiplier): Indicates the power of 10 by which the first two digits should be multiplied. 4.Fourth Band (Tolerance): Indicates the tolerance or accuracy of the resistor.  Resistance is inversely proportional to the cross- sectional area of the conductor. Wider conductors allow more electrons to flow simultaneously, reducing resistance.  The resistance of a conductor is directly proportional to its length. Longer conductors have more collisions between electrons and atoms, increasing resistance. R = Resistance p = Resistivity L = Length A - Area cross- section  For most conductors (e.g., metals), resistance increases with temperature because atomic vibrations become more intense, leading to more collisions with electrons. For some materials (e.g., semiconductors), resistance decreases A material exhibits ohmic resistance if it follows Ohm's Law, which states that the current (I) through a conductor is directly proportional to the applied voltage (V) Characteristics: The resistance (R) is constant and independent of the applied voltage or current. The V-I graph is a straight line passing through the origin, indicating linear behavior. Formula: R - Resistor V - Voltage An electric flat iron draws a current of 15 A when connected to a 110 V line. (a) Assuming that the heating element of flat iron obeys Ohm’s Law, what is its resistance? (b) What is the resistivity of the heating element if it is a wire that is 2.5 cm long with a  A 10 Ω resistor is connected across a 20 V power supply. Determine the current flowing through the resistor. A circuit consists of a 15 Ω resistor connected to a 12 V battery. What is the current flowing through the resistor? A material exhibits non-ohmic resistance if it does not follow Ohm's Law. The current through the material does not vary linearly with the applied voltage. Characteristics: The resistance varies with the applied voltage, current, or other conditions like temperature. The V-I graph is non-linear, showing a curve instead of  Electric current flow along a wire is similar to water flow in a pipe. To flow, a potential difference is needed. Common sources of potential difference include electric batteries, solar cells, fuel cells, and generators.  Cells consist of two electrodes and electrolytes. Cathode connected to positive terminal, anode to negative. Oxidation reaction at anode releases electrons. Electrons travel to cathode for reduction reaction. Electrolyte transports ions between electrodes.  The power expanded in an appliances is the rate at which it consumes electrical energy. Electric power is obtained by multiplying the voltage by the current. Power rating of appliances marked on back or bottom. Higher wattage indicates higher electrical energy consumption. Electric bill pays for electricity consumption, not power. Determined by multiplying appliance's power rating by time switched on.  A person used his 1500 W air conditioning unit for 5 hrs every day during the month of June. How much did using his air conditioner cost him if electricity is priced at P8.1/kW.h?  A compact fluorescent lamp (CFL) uses less energy than its equivalent incandescent bulb. How much will a person save if she/he uses a 20 W CFL instead of a 100 W incandescent lamp for 6 hrs in 30 days? Electricity is priced at  An ammeter is a device used for measuring current. It is always connected in series with the circuit element to which the current is to be determined. An ammeter is connected by opening the circuit and then inserting it in line or in series with the circuit. An  A voltmeter is a device that measures the electromotive force or potential difference between two points in a circuit. A voltmeter is connected across or parallel to the part of the circuit element where potential difference is to be determined. A voltmeter is  Household circuitry consists of parallel circuits parallel to the main power line. Overuse of appliances can lead to circuit overload, causing wires to heat up and cause fire. To prevent overloading, fuses or circuit breakers are inserted in circuits. Fuses are high-resistance alloy strips that melt readily when the current exceeds 15 A. Circuit breakers are switches that automatically open when the current is large, causing the fuse to blow up and the circuit breaker to trip.