Current Electricity Test. 1

A balanced bridge means the potential at the two points connected by the galvanometer is equal, resulting in zero current flow through it.

The Ohm (Ω) is the SI unit of electrical resistance, named after German physicist Georg Ohm.

First, find the power using P = V²/R = (200)² / 50 = 40000 / 50 = 800 W. Then, heat energy H = Power × time = 800 W × 30 s = 24000 J.

Electricity bills measure energy consumption in kilowatt-hours (kWh). 1 kWh is the energy used by a 1kW appliance for 1 hour.

Conductivity (σ) is the measure of a material's ability to conduct electricity and is defined as the reciprocal of resistivity (σ = 1/ρ).

Electric power can be expressed in several ways, including P = VI, P = I²R, and P = V²/R. All are correct, but P = I²R is one of the options.

The bridge is balanced when the ratio of resistances in one pair of adjacent arms is equal to the ratio of resistances in the other pair.

By convention, the direction of current is taken as the direction of flow of positive charge, which is opposite to the direction of flow of electrons.

Ohm's law is stated as V = IR, which means for a constant resistance, voltage (potential difference) is directly proportional to the current (I).

In metals, increased temperature causes more vibrations of the lattice ions, leading to more frequent collisions with electrons and thus higher resistance.

EMF is the work done by a source (like a battery) to move a unit of charge around a complete circuit. Its unit is Volts (Joules/Coulomb).

From the formula R = ρ(L/A), if length L=1m and cross-sectional area A=1m², then resistance R becomes equal to resistivity ρ.

The junction rule states that the total current entering a junction equals the total current leaving it, which means charge is conserved.

1 kWh = 1000 Watts × 3600 seconds = 3,600,000 Joules = 3.6 × 10⁶ J.

When supplying current, a voltage drop (Ir) occurs across the internal resistance (r), so the terminal voltage is Vt = E - Ir.

The loop rule states that the sum of all potential changes in a closed loop is zero, reflecting the principle of conservation of energy.

Using the potentiometer principle, E₁/E₂ = l₁/l₂. So, 1.25 V / E₂ = 35 cm / 63 cm. This gives E₂ = 1.25 * (63/35) = 1.25 * 1.8 = 2.25 V.

At the null/balance point, the potentiometer draws no current, so it measures the true EMF without any potential drop due to internal resistance.

Brown=1, Black=0, Orange multiplier=10³. This gives 10 × 10³ Ω = 10,000 Ω or 10 kΩ. The Gold band indicates a tolerance of ±5%.

A thermistor is a type of resistor whose resistance is designed to be highly dependent on temperature, making it useful as a temperature sensor.