Current Electricity Test. 3

A potential divider uses series resistors to provide a fraction of the input voltage as an output, which can be fixed or variable.

A fuse needs high resistance to heat up effectively (P=I²R) with excess current, and a low melting point to break the circuit before damage occurs.

Current I = Q/t = (ne)/t. Q = 10⁷ × (1.6 × 10⁻¹⁹ C) = 1.6 × 10⁻¹² C. Since t=1s, the current is 1.6 × 10⁻¹² A.

A high resistance (multiplier) is connected in series to limit the current and allow the galvanometer to measure a large potential difference across the combination.

The temperature at which a material's resistance abruptly drops to zero is known as its critical temperature (Tc).

Joule's law of heating states that the heat produced in a resistor is proportional to the square of the current, the resistance, and the time (H = I²Rt).

From Ohm's law V = IR, if V is on the y-axis and I is on the x-axis, the slope (ΔV/ΔI) is equal to the resistance R.

Total resistance R_total = R_ext + r = 4Ω + 1Ω = 5Ω. Current I = E / R_total = 10V / 5Ω = 2A.

Yellow=4, Violet=7, Red multiplier=10². This gives 47 × 10² = 4700 Ω = 4.7 kΩ.

Alloys like Manganin are used because they have high resistivity and a very low temperature coefficient of resistance, ensuring a stable potential gradient.

Terminal potential difference Vt = E - Ir = 10V - (2A)(1Ω) = 8V. Alternatively, it's the voltage across the external resistor: Vt = I * R_ext = 2A * 4Ω = 8V.

The series combination gives R_series = 10 Ω + 30 Ω = 40 Ω. This is in parallel with 20 Ω. The equivalent resistance Req is 1/Req = 1/40 + 1/20 = (1+2)/40 = 3/40. So, Req = 40/3 ≈ 13.33 Ω.

Current I = Q/t. Time must be in seconds: 5 minutes = 300 s. So, I = 600 C / 300 s = 2 A.

A low-resistance shunt is connected in parallel to divert most of the current, allowing the sensitive galvanometer to measure a small fraction of the total current.

Between any two vertices, two resistors are in series (3+3=6Ω), and this combination is in parallel with the third resistor (3Ω). 1/Req = 1/6 + 1/3 = 3/6 = 1/2. So, Req = 2Ω.

Conductivity is the reciprocal of resistivity (Ω-m). Its unit is 1/(Ω-m), which is also called Siemens per meter (S/m).

Original resistance R = ρ(L/A). New resistance R' = ρ((L/2)/(2A)) = (1/4) * ρ(L/A) = R/4.

Increasing the temperature of a semiconductor provides energy to release more charge carriers (electrons and holes), thus increasing its conductivity and decreasing its resistance.

In the absence of an external electric field, the random velocities of electrons are in all directions and cancel each other out, resulting in no net flow of charge.

Drift velocity is directly proportional to the electric field (E), and E is directly proportional to the potential difference (V). Therefore, doubling V doubles the drift velocity.