Physics Current Electricity

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.

Resistance is referred to the ability of an object to oppose the flow of electric current through itself. On the other hand, resistivity is the property of that particular material of resisting the passage of electric current over a particular unit area. Resistance has SI unit ohm whereas resistivity has ohm-metre.

The primary reason for this is that silver is a quite expensive material to be used on such a large scale. Also, it doesn't have a much longer lifespan and tarnishes easily. So copper is used for electrical wiring because it offers low resistance to electric current is comparatively much more safer option to be commercially used.