* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Regenerative circuit wikipedia , lookup
Lumped element model wikipedia , lookup
Thermal runaway wikipedia , lookup
Power electronics wikipedia , lookup
Valve RF amplifier wikipedia , lookup
Schmitt trigger wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Negative resistance wikipedia , lookup
Operational amplifier wikipedia , lookup
Two-port network wikipedia , lookup
Power MOSFET wikipedia , lookup
Electrical ballast wikipedia , lookup
Surge protector wikipedia , lookup
RLC circuit wikipedia , lookup
Rectiverter wikipedia , lookup
Current source wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Opto-isolator wikipedia , lookup
Network analysis (electrical circuits) wikipedia , lookup
Simple Electric Circuits Menu • Circuit Symbols • Current • Voltage • Resistance • Summary Table Circuit Symbols Identify the Circuit Symbols A Cell A Filament lamp/ Bulb A Battery of 2 Cells A Switch A Battery of a number of cells A fixed Resistor Identify the Symbols Variable Resistor L.D.R Thermistor Fuse Heater Loudspeaker Identify the Circuit Symbols A V M Ammeter Voltmeter Motor L.E.D Draw the Circuit Symbols Component Circuit Symbol Thermistor L.D.R Fuse L.E.D Return to menu Current Electrons Flow in the Opposite way to the Conventional Current -+ Electrons are negatively charged and therefore flow from negative to positive e- We normally say that the current flows from positive to negative Current Current is the FLOW OF ELECTRONS AROUND A CIRCUIT In metals, current is carried by electrons The unit of current is the ampere (A) We use an ammeter to measure current Ampere This is the scientist AMPERE. He studied current in circuits and gave his name to the unit of current Current in a Series Circuit 2A 2A 2A The Current in a Series Circuit is the Same at Every Point In a series circuit the bulbs are all the same brightness If the bulbs are of the same rating! Current Questions A B C 1) The current reading for bulb B is 2A. What are the readings for bulbs A and C? 2) Bulb suddenly fails. What happens to bulbs A and C? What Is the Current at This Point? 6A Brightness of Bulbs in a Series Circuit If a cell is added the current will increase and the bulb gets brighter Brightness of Bulbs in a Series Circuit If a bulb is added the current will decrease as there is greater resistance in the circuit and the bulbs get dimmer Current in a Parallel Circuit A PARALLEL circuit has more than one path for the current to flow through Bulb A Bulb B Assuming both bulbs are the Same…they will be the same brightness Current in a Parallel Circuit The Advantages of a parallel circuit are: Bulb A Bulb B • If one bulb fails ….the other will remain on • Both bulbs can be switched on separately Current in a Parallel Circuit 6A 2A 2A 2A 6A The total flow of current is equal to the total current from all of the branches What is the ammeter reading? 9A 3A 3A 3A Return to menu Voltage (Potential Difference) Voltage Is the Driving Force That Pushes the Current Around the Circuit We need Energy to push the electrons around the circuit. In this case the energy comes from the lemon (in the form of chemical energy) Potential Difference/ Voltage This is VOLTA. He studied the driving force that pushes current around a circuit. He gave his name to the unit of Potential Difference The unit of Potential Difference is the VOLT (V) Voltage in a Series Circuit 12V 4V 4V 12V 4V The voltage in a series circuit is shared across each component. The sum of the voltages across each component equals the source voltage What Is the Voltage? ?V 8V 8V ?V 8V 6V 6V 6V Voltage in a Parallel Circuit The voltage is the same across all components in parallel 9V What Is the Voltage? ?V ?V Return to menu Resistance Resistance Resistance is anything in a circuit that restricts the flow of current It can be calculated using Ohm’s Law: Resistance = (Ohms) The unit of Resistance is the Ohm Voltage (V) V Current (A) I x R Complete the meter readings 6A 12V A2 A3 V1 A1 V2 V3 Calculate the resistance ? 12V 3A Current-Voltage Graphs Show Resistance A Resistor at constant temperature I V Different wires have different resistances The current through a resistor at constant temperature is proportional to the voltage Current-Voltage Graphs Show Resistance I V A Filament Bulb As the temperature of the filament increases, the resistance increases – hence the curve Current-Voltage Graphs Show Resistance Current will only flow through in ONE DIRECTION I V A Diode (It has very high resistance in the reverse direction) Resistance in Wires – Cross Sectional Area Thin wires have more resistance than thick wires Halving the cross sectional area of a wire doubles its resistance because there is half as much space for the electrons to move Resistance - Length of Wire Doubling the Length of a wire Doubles its resistance because the electrons have twice as far to move Resistance - Material Different materials have different resistances. For Example: A nichrome wire has more resistance than a copper wire of the same size (the atoms in nichrome hold the electrons more tightly than copper atoms) Dark 1A The Light Dependent Resistor Light 5A The resistance of the LDR depends on the amount of light falling on it. Its resistance decreases as the amount of light falling on it increases The Thermistor 1A COLD 5A WARM The resistance of a thermistor depends on its temperature. Its resistance decreases as the temperature of the thermistor increases Explain Fully How the Following Work 1) A Diode 2) A Thermistor 3) A Light Dependent Resistor Return to Menu Summary: Current, Voltage, Resistance, Series & Parallel How are voltmeters & Ammeter connected in a circuit? A Ammeters are always connected in SERIES Voltmeters are always connected in Parallel V Summary Table Current Is the flow of electrons around a circuit Voltage Is the driving force that pushes the current around. Is anything in a circuit which slows the flow down Resistance There is a Balance…. If you increase the Voltage – then more current will flow If you increases the Resistance – then less current will flow Which Is the Series and Parallel Circuit A * Current is THE SAME at any point * Voltage SPLITS UP over each component B * Current SPLITS UP down each branch * Voltage is THE SAME across each branch Return to Menu