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ELECTRICAL COMPONENTS

ELECTRICAL COMPONENTS. Clicking on me will move you to the next page. BUTTONS. Clicking on me will take you to a list of equations, clicking on me again will take you back to the previous page. Click us;.

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ELECTRICAL COMPONENTS

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  1. ELECTRICAL COMPONENTS Clicking on me will move you to the next page. BUTTONS Clicking on me will take you to a list of equations, clicking on me again will take you back to the previous page. . Click us; Clicking on me will allow you to hear some information on the topic. Clicking on me again will stop the sound. Clicking on me will move you back a page. Clicking on me will reveal some information. Clicking on me will reveal an answer. TOPICS Jump to … Jump to … Clicking on me will bring you back to this page. Jump to… … the filament lamp (3 pages). Jump to … Jump to … … the diode (2 pages). Jump to … … the thermistor. Clicking on me will take you to SI multipliers table. Clicking on me again will take you back to the page you were on previously. … the LDR – light dependent resistor. …practice question. …exam question (2 pages).

  2. LAMP MEASURING CIRCUIT THE CIRCUITS Variable D.C. supply 12 V D.C. supply _ _ + + V V Ammeter in series Ammeter in the flow Variable resistor A A Voltmeter across Voltmeter in parallel THE GRAPH

  3. FILAMENT LAMP GRAPH THE GRAPH V (volt) I (mA) 2 4 6 8 10 12 20 42 53 67 71 80 RESISTANCE R = V = 5 V = 5V = 109 I46 mA 0.046A R = V = 10 V = 10V = 132 I72 mA 0.072A As the voltage across the lamp increases the currentincreases also. As the current increases the lamp becomes brighter and hotter. As the current increases the resistance of the lamp increases also.

  4. LAMP GRAPH EXPLANATION Hot, bright wire; higher resistance Molecules vibrating more Molecules in a hot wire. Less space for the electrons to pass gives a greater resistance. Molecules in a cold wire. Molecules vibrating a little bit. Cold, dark wire; smaller resistance Plenty of space for the electrons to pass so a smaller resistance.

  5. DIODE GRAPH Symbol Component Diode I (mA) V (volt) I (Current/mA) _ + 8 0.1 0.2 0.3 0.4 0.5 0.60.7 0 0 0 0 0.1 1.3 8.0 Direction of current Direction of current 6 V 4 A 0 amp 2 0 0.6 0.4 0.8 0.2 -V V (Voltage) 8 folt 2 volt 6 folt 4 folt Circuit _ + Graph -I Resistance Low resistance Conductor High Resistance Insulator

  6. THERMISTOR Multimeter usedasOhm-meter measures resistance directly. Symbol The resistance of the thermistor decreases as the temperature increases. Thermometer Resistance water Thermistor Use of THERMISTORSControlling temperature of freezer, toasters, hair dryers etcFire alarms HEAT THE WATER Temperature HEAT

  7. LDR - LIGHT DEPENDENT RESISTOR The resistance of an LDR yn reduces as the brightness increases. NIGHT DAY LDR Multimeter usedasOhm-meter measure resistance directly. Symbol Highresistance Lowresistance Resistance Light intensity USE OF LDR - Controlling streetlighting, deciding when to use a flash with the camera on your phone.

  8. PRACTICE QUESTION _ + _ + _ + _ _ _ + + + Click on the lamp that would light up in these circuits.

  9. EXAM QUESTION 1 2 Resistance = voltage = 6V = 3 current 2A 3 Current through W = 1.25 A from graphCerrynt A1 = A2 + A3 = 3 + 1.25 = 4.25 A 4.25 lamp resistance = wire resistance Resistance is equal to voltage over current. The lamp and the wire have the same voltage and current and so must have the same resistance. WJEC: Physics 2 Jan 2013 (Higher) Q.1

  10. EXAM QUESTION 2 6.1 Close values are ok as well. Resistance = voltage = 0.7V = 5.83 current 0.12A Moving the slider on the variable resistor changes the resistance of the circuit which produces a variable voltage and current at the diode. 5.8 The current is reduced to almost zero. The resistance of the diode at a volatage of 0.6 is equal to 0.6V/0 A = . The resistance increases to a very high value. Yoou can use a small value here e.g. 6V/0.001 = 6000 . It’s the idea of a very large resistance that’s important here. WJEC: Physics 2 Jan 2011 (Higher) Q.5

  11. EQUATIONS higher higher Open the file “Maths for Physics” for more about the use of mathematics in Physics.

  12. SI MULTIPLIERS k - kilo p - pico n - nano M - mega G - giga  - micro m - milli T - tera You only see the letter of the prefix on an exam paper, NOT the name. On a Foundation paper only milli, kilo a mega are used.

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