What is charge carrier density?

In the figure shown, what is the current (in ampere) drawn from the battery? You are given:
$R_1=15 \mathrm{\Omega }\mathrm{ }, R_2=10 \mathrm{\Omega }\mathrm{ }, R_3=20 \mathrm{\Omega }\mathrm{ }, R_4=5 \mathrm{\Omega },\mathrm{ }{R}_5=25 \mathrm{\Omega },\mathrm{ }{R}_6=30 \mathrm{\Omega },\mathrm{ }E=15 \mathrm{V}$

An ideal ammeter is connected to a battery as shown in the figure. The currents through the $5.0 \mathrm{\Omega }$ resistor and the $2.0 \mathrm{\Omega }$ resistor are, respectively

In the circuit shown below, a student performing Ohm's law experiment accidentally puts the voltmeter and the ammeter as shown in the circuit below; the reading in the voltmeter will be close to

Find the potential difference between $a$ and $b$, as shown in the below circuit.

$I-V$ characteristic of a copper wire of length $L$ and area of cross-section $A$ is shown in figure. The slope of the curve becomes

As shown in the schematic below, a rod of uniform cross-sectional area $A$ and length $l$ is carrying a constant current $i$ through it and voltage across the rod is measured using an ideal voltmeter. The rod is stretched by the application of a force $F$.

Which of the following graphs would show the variation in the voltage across the rod as function of the strain $\epsilon$ when the strain is small. Neglect Joule heating.