Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Ohm’s Law & Electrical Power Resistance • Resistance - the tendency for a material to oppose the flow of electrons - All materials have some electrical resistance. - Resistance depends on length, crosssectional area, material, and temperature Ex. Making wires thinner, longer, or hotter increases the resistance. Resistors • Resistors provide a specified amount or resistance to a conductor. • Used to regulate the amount of current in a conductor. Ohm’s Law • Ohm’s law - the current in a circuit (I) equals the voltage difference (V) divided by the resistance (R). R = V/I • Resistance is measured in ohms (). Sample Problem The resistance of a steam iron is 19.0 Ω. What is the current in the iron when it is connected across a potential difference of 120 V? R = V/I V= 120 V R= 19 Ω I = V/R= 120 V / 19 Ω = 6.32 A Electrical Power • Electrical Power is the rate at which electric charge converts electrical potential energy to non-electrical forms of energy. P = IΔV = I²R = ΔV²/R SI Unit = watt (W) Sample Problem An electric space heater is connected across a 120 V outlet. The heater dissipates 1320 W of power in the form of electromagnetic radiation and heat. Calculate the resistance of the heater. P = ΔV²/R P = 1320 W V= 120 V R = ΔV²/P = (120 V)²/ 1320 W = 10.9 Ω Electric Power • Electric companies measure energy consumed in kilowatt-hours (kW •h) Electric Power How much does it cost to operate a 100.0 W light bulb for 24 h if electrical energy costs $0.080 per kW•h? Total Energy Used = (0.100 kW)( 24 h) = 2.4 kW•h Cost = (2.4 kW•h)($ 0.080/ kW•h) = $0.19