Presentation on theme: "Chapter 17.2 – Current electrical potential energy –"— Presentation transcript:
1 Chapter 17.2 – Current electrical potential energy – the ability to move an electric charge from one point to anotherfor like charges, potential increases as charges move closerfor unlike charges, potential decreases as charges move closer
2 Chapter 17.2 – Current potential difference – the change in electrical potential energy divided by the charge that moves through the electric fieldmeasured in units of volts (V)often called voltageoutlets have a voltage of 120 V
3 Chapter 17.2 – Current Batteries the ends of a battery are called terminalsthere is a potential difference between terminals of a batterybatteries are made of electrochemical cells – devices that convert chemical energy to electrical energythe cells contain an electrolyte – a solution that conducts electricityeach cell has 2 electrodes – a conductor used to make contact with the electrolyte
4 Chapter 17.2 – Current there are 2 kinds of batteries dry cell – has a moist pastelike electrolytetypically 1.5 Vex. AA, AAA batteries, cell phone & laptop batterieswet cell –has a liquid electrolytetypically 12 Vex. car battery
5 Chapter 17.2 – Current electric current – rate at which charges pass through a given point or conductormeasured in amperes (A)batteries produce a current by creating a potential difference across an electrical devicethe electric field pushes electrons toward the side with lower potential
6 Chapter 17.2 – Currentdirect current (DC) – electrons always move from one terminal to the other in the same direction ex. batteries alternating current (AC) – electrons constantly change direction between terminals ex. wall socket
7 Chapter 17.2 – Current conventional current – current made of positive charge that has the same effect as the actual motion of chargethe direction of conventional current is opposite the direction that electrons moveresistance –opposition to the movement of a current by a material or devicecaused by internal friction which slows the movement of chargesunits of ohms (Ω)
8 Chapter 17.2 – Current resistance can be found from Ohm’s law 𝑟𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒= 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑅= 𝑉 𝐼another way is to write V = IRunits: volts = amps ∙ ohmsex. Find the resistance of a lantern that uses a 24 V power supply and draws a current of 0.80 A.
9 Chapter 17.2 – CurrentThe current in a resistor is 0.50 A when connected across a voltage of 120 V. What is the resistance of the resistor? A 1.5 V battery is connected to a light bulb with a resistance of 3.5 Ω. What is the current in the bulb?
10 Chapter 17.2 – Current conductors have a low resistance insulators have a high resistancesemiconductor –has properties between conductors and insulatorsex. used in computers, cell phones, anything with a microchipsuperconductor –material with zero resistance when their temperature falls below a critical temperaturevery cold temperatures (-272°C to -123°C) are used to make powerful magnets to levitate trains
11 Chapter 17.2 – Currentground wire – wire connected to the ground which carries excess charge to the ground where it spreads out safely ex. third prong on power outlets