SECTION B: ACTIVITIES ACTIVITY AIM To identify a diode, an LED, a resistor and a capacit i ic such items. rpacitor from a mixed collection of APPARATUS AND MATERIAL REQUIRED A multimeter, a mixed collection of diode, LED, resistor and capacitor. [ratory Diode. A two termirial device which conducts current when forward biased and not when reverse biased. It does not emit light during its conduction. LED. A light emitting diode is a two terminal device which conducts current when forward biased and not when reverse biased. It emits a characteristic light during its conduction. Resistor. A two terminal device which conducts equally in both directions. Capacitor. A two terminal device which offers infinite resistance to de but has a finite reactance for ac. When connected across a de source, a multimeter shows a large current initially (for CC >uh) which decreases to zero quickly. This is because the capacitor initially draws a charge. [oucrams Diodes Carbon resistor Nate uD ev {L_ oan Be Paper ectrolytic a CAPACITORS Fig, 1 Diagrams of carbon resistor, diodes, LED and capacitors. Leoceoure 1L. Look for the colour bands on the given components. e ent is a resistor. 7 i fai band, then the component Sram ies cured el ‘ato common and positive terminals of the 2 nse la ad leads (or probes) i 1 : srt te lack and tends Pree eats gE MED 3. Touch the two probes to the two ends of each comp rest one oe ba ue desler deflection in the multimeter. Interchange the positions of two pl and again note the direction of deflection. Ifa component has a set of three colour™ LAB MANUAL PHYSICS-XIl 4. Ifthe muttimeter shows an equal defection in both directions, then the components an, 5. If a multimeter shows deflection in one direction without any emission of light fron component and no deflection in the opposite direction, then the component isa." 6 If the multimeter shows deflection in one direction alongwith the emission of light fron, component and no deflection in the opposite direction, then the component is an (p, 7. If the multimeter does not show any deflection on connecting its probes either Way, component, then the component is a capacitor. But if the capacitance ofthe capacitors in. the multimeter will show a large deflection initially which gradually decreases to zera, 8. Record all your observations in a tabular form. i OBSERVATIONS Table B1 : State of conduction of each component Ttem code State of conduction of a component Identified component A Conducts equally in both directions B Conducts in one direction without emission of light ic Conducts in one direction with emission of light D Does not conduct, gives an i decays to zero [Leesuur From the mixed grouping of components, the components marked A, B, C and D have been identified as resistor, diode, LED and capacitor respectively. I PRECAUTIONS 1. While checking the conduction state of any component, clean its leads properly. 2. Use the selector switch of the multimeter in resistance mode with highest range option. 3. While testing any component, avoid touching the metal end of either of multimeter probe. Body resistance in parallel with the component resistance may create confusion about tht conduction state of the component. ode 5. How do the conduction states of an ordinary 4 and an LED differ ? ‘An ordinary diode conducts in forward bs" ‘Any material that has some resistance is called a resistor. 2 What is a linear resistor ? A linear resistor is one which obeys Ohm’s law or for which V-1 graph is a straight line passing through the origin What ts a non-ohimic device ? A device which does not obey Ohm's law is called a non-ohmic device, Semiconductor diodes, LEDs, etc ; are non-ohmic devices. + Does an ohmic resistor conduct equally tor both forward and reverse biasing ? Yes, an ohmic resistor conducts equally when current is passed in onw direction and then in nrvesctte without any emission of light while an LED conte in forward direction with emission of light hot conduct in reverse biasing, * How does a capacitor behave towards de? A capacitor does not conduct de. But a ap2 large capacitance shows an initial deflection Py ammeter which decays to zero quickly. This # charging of the capacitor. How does a capacitor behave towards 2¢7 A capacitor conducts ac. because 8 OF reactance | X,. = ——. | is finite against c