The electrical resistivities of four materials P, Q, R and S are given below:
$\begin{matrix}\text{P}&6.84\times10^{-8}\Omega\text{m}\\\text{Q}&1.70\times10^{-8}\Omega\text{m}\\\text{R}&1.0\times10^{15}\Omega\text{m}\\\text{S}&11.0\times10^{-7}\Omega\text{m}\end{matrix}$
Which material will you use for making:
Heating element of electric iron.
Connecting wires of electric iron.
Covering of connecting wires?
Give reason for your choice in each case.
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S; because it has high resistivity of $\frac{11}{10000000}\text{ohm\ m}$ (it is actually nichrome).
Q; because it has very low resistivity of $\frac{1.7}{100000000}\text{ohm\ m}$ (it is actually copper).
R; because it has very very high resistivity of$1.0\times100000000000000\ \text{ohm\ m}$ (it is actually rubber).
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The electrical resistivities of four materials $A, B, C$ and $D$ are given below:
$\text{A}\ -110\times10^{-8}\Omega\text{ m}$
$\text{B}-\ 1.0\times10^{10}\Omega\text{ m}$
$\text{C}-\ 10.0\times10^{-8}\Omega\text{ m}$
$\text{D}-\ 2.3\times10^{3}\Omega\text{ m}$
Which material is:
A resistance of $40$ ohms and one of $60$ ohms are arranged in series across $220$ volt supply. Find the heat in joules produced by this combination of resistances in half a minute.
Derive the expression for the heat produced due to a current ‘I’ flowing for a time interval ‘t’ through a resistor ‘R’ having a potential difference ‘V’ across its ends. With which name is this relation known?
What will be the resistance of a metal wire of length $2$ metres and area of cross-section $1.55 \times 10m $, if the resistivity of the metal be $2.8 \times 10 m?$
A p.d. of 6V is applied to two resistors of $3 Ω$ and $6 Ω$ connected in parallel. Calculate:
The combined resistance.
The current flowing in the main circuit.
The current flowing in the $3 Ω$ resistor.
The electrical resistivities of five substances A, B, C, D and E are given below:
$\begin{matrix}\text{B}&110\times10^{-8}\Omega\text{ m}\\\text{C}&2.60\times10^{-8}\Omega\text{ m}\\\text{D}&10.0\times10^{-8}\Omega\text{ m}\\\text{E}&1.70\times10^{-8}\Omega\text{ m}\end{matrix}$