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We careful when talking about other people. We should be very careful and attentive while speaking to others. We should see to it that the person being spoken to must hear and follow us. This can be achieved only by speaking clearly, frankly and sufficiently loudly. One should not make unpleasant comment about a person behind his back.

When those two vectors (voltage and current) attain (reaches) their maximum and minimum values simultaneously (at the same time), then those two quantities are said in-phase. Here between those quantities there is no angle. 

Alternating current is that type of electric current, which changes it’s magnetude and direction periodically.  

When two alternating quantities voltage and current do not reaches their maximum and minimum values simultaneously, then they are called out of phase. 

Soldering is the process of joining two metals with an alloy whose melting point is less that of the materials to be soldered. 

Soldering at high temperature using brass as solder is called brazing or hard soldering. 

The composition of the fine solder (soft solder) is tin 60% and lead 40%. Its melting point is 190°C and is widely used.  

The development of an AC quantity through different stages is known as Phase. The term phase refers to the number of separate individual voltage setup in an AC circuit. 

Average of all instantaneous values of emf or current over a half cycle is known as average value or mean value. 

Average value = 0.637 * E_max or I_max

One complete set of changes in value and direction of alternating quantity and emf or current is called a cycle. 

Phase angle is an angular displacement between two alternating quantities. Phase angle is measured in electrical degrees or radians.

Periodic time is the time taken to complete on cycle. Its symbol is ‘T’. For example Indian standard frequency is 50 cycles per second. So the periodic time T = 1/50 seconds. That is equal to 20 m seconds. 

The alternating quantity that attains its maximum value later than the other quantity is called the lagging quantity. 

When two quantities are out of phase by 180° electrical, then they are said to be anti-phase quantities.  

When the phase angle between two vectors is 90° electrical, then they are said to be quadrature quantity.

The alternating quantity that reaches its maximum value earlier than the other quantity is known as the leading quantity

The international ampere is defined as that steady current which, flowing through a solution of silver nitrate, deposits silver at the rate of 0.001118 gm/sec.  

Number of cycles per second is called frequency. 

The value of an alternating quantity at a particular instant is called instantaneous value. 

Instantaneous value of both the directions will all be squared up and will be added together. Then divide to get the average with the number of instantaneous values and find the square root of this average to calculate the R.M.S value of the emf or current.

 Or 

The R.M.S value of an alternating current or emf is equal to the same value of direct current (DC), which produces the same amount of heat with the same time when applied the DC through the same circuit as AC is produced. 

R.M.S value = maximum value / √2 = 1/√2 = 0.707. 

∴ R.M.S value or effective value = 0.707 * E_max or I_max

Vector quantity: 

A quantity, which has both the direction and magnitude is said to be a vector quantity. Examples are force, emf, current etc. 

Scalar quantity:

A scalar quantity is that, which has only magnitude but no direction. Examples are temperature, mass, volume etc.

It is the maximum value of an alternating quantity that can be obtained in any one direction.  

Flow of electrons in any conductor is called electric current. Its symbol is ‘I’ and measuring unit is Ampere measured by ammeter or ampere meter

The ratio of maximum value to the R.M.S value is known as crest factor. So the crest factor = maximum value / R.M.S value.

= E_max or I_max / (E_max or I_max / √2) 

= E_max or I_max * √2 / E_max or I_max = √2 = 1.414 

The ratio of the R.M.S value to the average value is called the form factor. 

The ratio of the R.M.S value to the average value is called the form factor. 

∴ Form factor = 0.707 * E_max or I_max : 0.637 * E_max or I_max 

= 0.707 * E_max or I_max / 0.637 * E_max or I_max 

= 1.11

So that R.M.S value = average value * 1.11 

Or average value = R.M.S value / 1.11

The international volt is defined as 1/1.0183 of the emf of a Weston cadmium cell. It is that difference of potential which, when applied to a conductor whose resistance is 1 (one) international ohm, will cause a current of 1 (one) international ampere to flow. 

The matter is defined as anything, which possesses weight and occupies space and can be in any of three forms solid, liquid or gaseous. The matter consists of three ingredients, which are protons, neutrons and electrons. 

The ratio of minimum fusing current and the current rating of fusing element is called the fusing factor. 

Fusing factor = minimum fusing current / current rating of fusing element. Its value is always more than 1 (one). 

Reflection and refraction are the phenomena of light when a ray of light is incident upon the surface separating two mediums. reflection takes place in the same medium through which the ray is incident whereas refraction takes in another medium. The speed of light depends upon the medium. That is, the speed of light depends upon the refractive index of the medium and mathematically given as,

n=cv

where n = refractive index

c = speed of light

v = speed of light in that medium.

So, as the reflection takes place in the same medium, therefore, there is no any change in the speed of light but refraction takes place in another medium, therefore, the speed of light changes its path and hence get bend while entering into another medium. For example, when we see a stick dipped partly into a glass of water we observe that stick is bent at the surface of the water.

The speed of electricity or electrons is 297842 km (186000 miles) per second. 

Static electricity means electricity at rest. If we join a charged conductor to another conductor, electricity flows from one to the other. This way an electric current is produced, which lasts for a moment only. Static electricity is no use. Rubbing of two different materials having different electrons produces this. 

Fuse is a weakest point in an electrical circuit, which melts when the excess current flows through it in the electrical circuit. The materials, which can be used in fuses, are tin, lead, zinc, silver, antimony, copper, and aluminium, etc.  

a. Battery (chemical source) 

b. Generator (magnetism) 

c. Thermocouple (heat generated) 

d. Light (photo electric or solar cell) 

e. Pressure (piezo electricity) 

f. Friction (static electricity) 

The effects of temperature on resistance are 

a. In certain pure metals such as gold, copper, silver, aluminium etc. the resistance increases with increasing temperature at fairly regular manner. Such metals possess positive temperature coefficient of resistance.

b. In certain materials (alloys) such as eureka, nichrome etc. the change in resistance due to increasing temperature is irregular and negligible for a considerable range of temperature. 

c. In case of certain materials belongs to insulators, electrolytes such as paper, rubber, glass, mica, carbon, acids, alkalies etc. the resistance decreases with increasing temperature at fairly regular manner. Such materials posses negative coefficient of resistance.