Question

In the experiment identify diode, an LED, a transistor, an IC, a resistor and a capacitor from a mixed collection of such items. When the switch is on the battery eliminator the movement of the multimeter pointer given in column \(\mathrm{A}\), and electronic components name given in column \(\mathrm{B}\). \begin{tabular}{c|c} \(\frac{\text { Column A }}{\text { (1) If pointer moves when voltage is applied }}\) & Column B \\ (a) a LED \end{tabular} in one way and does not move when reversed and there is no light emission (2) If pointer moves when voltage is applied (b) a capacitor in one way and does not move when reverse and there is light emission (3) If pointer moves when voltage is applied (c) a diode in one way and also when reversed (4) If pointer does not move when voltage is (d) a resistor applied in one way and also when reversed (e) a transistor (A) \(1 \rightarrow \mathrm{a}, 2 \rightarrow \mathrm{d}, 3 \rightarrow \mathrm{e}, 4 \rightarrow \mathrm{c}\) (B) \(1 \rightarrow \mathrm{b}, 2 \rightarrow \mathrm{c}, 3 \rightarrow \mathrm{d}, 4 \rightarrow \mathrm{a}\) (C) \(1 \rightarrow \mathrm{c}, 2 \rightarrow \mathrm{a}, 3 \rightarrow \mathrm{d}, 4 \rightarrow \mathrm{b}\) (D) \(1 \rightarrow \mathrm{d}, 2 \rightarrow \mathrm{b}, 3 \rightarrow \mathrm{a}, 4 \rightarrow \mathrm{d}\)

Short answer

The short answer is: (B) 1 → b, 2 → c, 3 → d, 4 → a.

Step-by-step solution

LED

An LED (Light Emitting Diode) allows the current to pass in one direction only and emits light. In the given information, option (b) Capacitor is the only one that mentions light emission. Therefore, LED corresponds to observation 2.

Capacitor

A capacitor allows a current to flow when the voltage is applied and blocks it when fully charged. No light emission for capacitors. In the given information, option (a) LED exhibits a similar behavior but without light emission. Therefore, Capacitor corresponds to observation 1.

Diode

A diode allows current to flow in one direction only. No light emission for diodes. In this case, option (c), with the pointer moving in one direction only, best suits the behavior of a diode. Hence, Diode corresponds to observation 3.

Resistor

A resistor opposes the flow of current, but allows it to pass in both directions. The pointer should move in both directions when voltage is applied. None of the given observations match the behavior of a resistor perfectly. Since a transistor is associated with observation 3, we will assign Resistor to observation 4.

Transistor

A transistor allows current to flow based on a control voltage. Observation 3, where the pointer moves in one direction only, also when reversed, is the closest match for a transistor. Thus, Transistor corresponds to observation 3. Now, let's link the observations to the correct components: 1 → a (Capacitor) 2 → b (LED) 3 → c (Diode) 4 → d (Resistor) - → e (Transistor) Comparing our findings with the given options: (A) 1 → a, 2 → d, 3 → e, 4 → c (B) 1 → b, 2 → c, 3 → d, 4 → a (C) 1 → c, 2 → a, 3 → d, 4 → b (D) 1 → d, 2 → b, 3 → a, 4 → d The correct answer is (B) 1 → b, 2 → c, 3 → d, 4 → a.

Key concepts

Diode

Diodes are fundamental electronic components used to control the direction of current flow. They allow current to pass through them in only one direction, making them critical in converting alternating current (AC) to direct current (DC). This property is known as rectification. Diodes are typically marked with a line on one end, indicating the cathode, helping to ensure they are placed in the correct orientation in a circuit.
When using a multimeter to test a diode, you should expect the meter to show high resistance in one direction (reverse-biased) and low resistance in the other (forward-biased). This directional flow of current is vital for protecting circuits by preventing reverse voltage which could damage other components. Although diodes do not emit light themselves, they can be combined with other components, like LEDs, to create visible indicators.

Capacitor

Capacitors are passive electronic components that store and release electrical energy. They are widely used in electronic circuits for various purposes, such as filtering, buffering, and smoothing. A capacitor consists of two conductive plates separated by an insulating material called the dielectric. When voltage is applied across the plates, an electric field develops, storing energy.
In a practical setting, capacitors help stabilize power supply voltages, protect components from voltage spikes, and smoothen signal ripples. They allow current to pass when first applying a voltage, but as they charge, they resist further current flow, acting temporarily like a battery. When observing a capacitor with a multimeter, you might notice that the pointer moves initially but then stops as the capacitor charges.
Capacitors are identified by their capacitance in microfarads (µF) or nanofarads (nF) and have polarity for some specific types, such as electrolytic capacitors. Proper orientation is crucial for these polarized capacitors to prevent damage.

Resistor

Resistors are ubiquitous in electronic circuits, primarily used to resist the flow of electric current and adjust voltage levels within a circuit. They function according to Ohm's Law, which states that the voltage across a resistor is proportional to the current flowing through it, with the relationship defined by the resistance value in ohms (Ω).
Resistors come in various forms, from fixed to variable types (like potentiometers) and are often color-coded to indicate resistance value, tolerance, and sometimes reliability. They play a pivotal role in simple operations, such as limiting current through LEDs or dividing voltages across components in a circuit.
When measured with a multimeter, the resistance will show consistent readings irrespective of polarity. This indicates that resistors allow current to flow freely in both directions, unlike diodes.

Transistor

Transistors are active components essential for the functioning of modern electronics. They can act as switches or amplifiers in circuitry. Comprised of semiconductor materials, transistors work by using a small input current to control a larger output current. The most common types of transistors are bipolar junction transistors (BJTs) and field-effect transistors (FETs).
A transistor usually has three terminals: the emitter, the base, and the collector in BJTs or the source, the gate, and the drain in FETs. These terminals allow the transistor to control electrical signals through appropriate biasing, providing a versatile means of influencing the behavior of circuits.
When testing a transistor with a multimeter, be sure to check the device’s datasheet to ensure proper pin identification and expected voltages or currents. A healthy transistor should demonstrate clear amplification of signals or switching action as dictated by its design.

LED

Light Emitting Diodes (LEDs) are specialized diodes that emit light when a current passes through them in the forward direction. They are used extensively as indicators due to their energy efficiency and long lifespan. These components are typically manufactured to emit visible light in a range of colors, determined by the materials used in the semiconductor.
LEDs are polar components similar to standard diodes, requiring the correct orientation to function properly. The longer lead indicates the anode (positive side), while the shorter lead indicates the cathode (negative side). In an experimental setup, an LED can illuminate when the current flow is correctly directed, distinguishing it from other components like capacitors and resistors.
LEDs consume very little power, making them perfect for battery-powered devices, backlighting solutions, and decorative lighting applications. Testing an LED with a multimeter typically shows low resistance when forward-biased and high resistance (or no conduction) when reverse-biased.