Physics Current Electricity

According to this chapter, a galvanometer is used to find and measure the small electric currents in a circuit. The principle that works in a galvanometer is the electromagnetic induction.

There are two types of electricity - Static and Current electricity. The electric charges buildup on a material's surface is called the static electricity. The continuous flow of electric charge is termed as the current electricity. Current electricity is of two types - Alternating Current (AC) and Direct Current (DC). In AC, the charge direction reverses periodically and in DC, charge flows in one direction.

The current's SI unit is ampere. The symbol for ampere is A. The term ampere is named after the French physicist André-Marie Ampère.

In simple words, current electricity can be defined as the electric charge continuously moving from one place to another along a pathway. It is measured in amperes (A). Electric current is needed for electrical devices to work.

No, in fact, it is one of the easiest chapter of class 12 Physics. Other chapters which are considered comparatively easy are Ray Optics and Electric Charges and Fields.

Resistance of whole wire is

$R=r^{\text{'}}*l$

$20=1*l$

$l=20m$

Let length of the shorter section = a

$\frac{1}{R}=\frac{1}{a}+\frac{1}{\left(20-a\right)}$

$\frac{1}{1.8}=\frac{20-a+a}{a\left(20-a\right)}?20a-a^2=36$

$a=2and18$

$?a=2m$

(Explanation can be elaborate)

$l=\frac{25}{R_{eq}}$

$R_{eq}=25\mathrm{\Omega }$

$l=\frac{25}{25}1A$

Let V  be the potential of the junction as shown in figure. Applying junction law, we have

or $\frac{20-V}{2}+\frac{5-V}{4}\overline{\to }\frac{V-0}{2}$

or $40-2V+5-V=2V$ or $5V=45\Rightarrow V=9V$

$\therefore i_3=\frac{V}{2}=4.5A$

Please consider the following Image  

Yes, a material's resistivity will increase with the presence of impurities. This is because these impurities will occupy more surface area and disrupt the flow of electrons which will impact their free movement. As a result, the current cannot pass freely through the material and it will affect the resistivity.