# Physics Study Guide/Electronics

## Contents

Electronics is the application of electromagnetic (and quantum) theory to construct devices that can perform useful tasks, from as simple as electrical heaters or light bulbs to as complex as the Large Hadron Collider.

Electronics;component of electronics

# Electronics

## Introduction

To discuss electronics we need the basic concepts from electricity: charge, current which is flow of charge, and potential which is the potential energy difference between two places. Please make sure these concepts are familiar before continuing.

## Circuits

The interest of electronics is circuits. A circuit consists of wires' that connect components. Typical components are resistors, voltage sources. In order to maintain a constant electrical current a continued exhaustion of chemical or mechanical energy is required.

A voltaic cell is a common electromotive power source for a circuit. It consists primarily of two plates, a positive copper plate and a negative zinc plate. One must note that the plates are placed in dilute sulfuric acid. Whence a key is switched or the circuit is closed the zinc reacts with the sulfuric in which it is placed in. One may discern that the electromotive force which is then applied to the circuit is believed to be converted from chemical to electrical energy upon the surface of the zinc cell. Whence the E.M.F is converted from chemical to electrical energy the electromotive force travels through the sulfuric acid. However disadvantages occur whence utilizing a voltaic or galvanic cell. Whence the circuit is closed, simultaneously hydrogen bubbles accumulate upon the copper plate surface hence decreasing the total electromotive power source applied to the circuit in question. The resistance with which the electromotive source encounters as it flows form the zinc plate to the copper plate through the dilute sulfuric acid is distinguished as internal resistance. Hence the voltaic cell uses diluted rather than concentrated sulfuric acid so as to reduce the internal resistance present inside of the component which applies the electromotive force to the circuit.

A circuit can be open, when there is a break so that no current can flow, or it can be closed, so that current can flow. These definitions allow us to discuss electronics efficiently.

## Direct current and alternating Current

When the Electrons moves through a particular medium in straight without oscillating on their mean position then it is Direct Current. This DC is used in almost every electronical component. Alternating Current on the other hand as the name suggest, the Electrons alter back and forth and hence produces much electrical energy. AC is mainly used to reduce the wastage of electrons and passing much energy at one time.

## Ohm's law

If 'V' is Potential Difference applied at two ends of conductor and 'I' is Current flowing through the conductor then 'I' is directly proportional to its 'V'. V = I x R

## Kirchoff's laws

Kirchoff's laws generally hold for direct current (DC) circuits, but fail when dealing with changing electric current and voltage such as alternating current (AC) or signal processing in combination with capacitors, inductors, and antennas.

### Kirchoff's current law

The sum of all the currents entering and leaving any point in a circuit is equal to zero.

$\sum _{k=1}^{n}I_{k}=0$

It is based on the assumption that current flows only in conductors, and that whenever current flows into one end of a conductor it immediately flows out the other end.

### Kirchoff's voltage law

The sum of all the voltages around the circuit loop is equal to zero.

$\sum _{k=1}^{n}V_{k}=0$

It is based on the assumption that there is no fluctuating magnetic field linking the closed circuit loop.

## Power

p=work done/time taken p=I*V (current * Voltage) Other Equations for P can also be derived using Ohm's Law, such as P = IR^2, because V=IR, which can be plugged in to get P= I * (IR) and another equation being P = V^2/R.

## Resistors in series

R$eq$ =R$1$ +R$2$ +R$3$ +--------

## Resistors in parallel

1/R = 1/R1+1/R2+1/R3+......

## Capacitors

 $C={Q \over V}$ $C_{\rm {series}}=\sum _{n}{1 \over C_{n}}={1 \over C_{1}}+{1 \over C_{2}}+{1 \over C_{3}}+\cdots +{1 \over C_{n}}$ $C_{\rm {parallel}}=\sum _{n}C_{n}=C_{1}+C_{2}+C_{3}+\cdots +C_{n}$ ## Semiconductors

 $I={\frac {Q}{T}}$ Current is the rate of flow of charge.

$I$  = Current [amperes - A]
$Q$  = Charge [coulombs - C]
$T$  = Time [seconds - s]

 $V=IR\$ Voltage is equal to current multiplied by resistance

Power is equal to the product of voltage and current

Electronics is the flow of current through semiconductor devices like silicon and germanium.

Semiconductor devices are those which behave like conductors at higher temperature.

Transistor, diode, SCR are some electronic devices.