## Measurement

This topic covers “Measurement” of A Level Physics. (Equivalent to Advanced Placement) If this is too advanced for you, you can try the more basic version here. Sub-topics Base Quantities Prefixes Scalar and vector quantities Systematic Error & Random Error Parallax Error & Zero Error, Accuracy & Precision Uncertainty Questions: (With worked solutions) Set 1 Questions kindly contributed by a reader: …

## Internal Resistance

Internal resistance (r) of any real source is the resistance that charge moving through the material of the source encounters. The presence of internal resistance in a source of electromotive force means that the potential difference across the terminals of the electrical source (terminal potential difference) is always less than its electromotive force. By conservation of energy, Energy delivered by …

## Electromotive Force

The electromotive force ($\epsilon$) of a source is the energy converted from other forms to electrical per unit charge delivered round a complete circuit. $\epsilon = \frac{E}{Q}$ , where $\epsilon$ is electromotive force (Units: V), E is energy converted, Q is charge Difference between electromotive force and potential difference Electromotive Force of a source is the ability of the source to …

## I/V graph of Thermistor

Thermistor (Negative Temperature Coefficient Type, NTC) From the I-V curve, the ratio V/I decreases for increasing current. Resistance decreases with increasing current. Reason: The thermistor is a resistance element made of semiconductor material. Increased potential difference across the thermistor results in increased current which in turn causes the temperature to rise. As the temperature rise, the lattice ion’s vibration increases …

## I/V graph of Filament Lamp

Filament lamp From the I/V graph, the ratio V/I increases as current increases. Resistance of the filament lamp increase with temperature.   Reason: As the potential difference across a filament lamp increases, the current increases and the energy dissipated, as heat, increases, resulting in a higher temperature. As the temperature increases, resistance of the filament increases. The collision between the …

## I/V graph of a semiconductor diode

A diode is a device that has very low resistance in one direction and a very high resistance in the other direction. If a potential difference is applied across a diode in the direction with low resistance, it is said to be forward bias. If a potential difference is applied in the direction with very high resistance, it is said …

## I/V graph of metallic conductor

Metallic conductors at constant temperature The I-V graph of metallic conductor is a straight line pass through the origin. They obey Ohm’s Law, having resistance that is independent of current. (Ohmic conductors) Reason: Resistance in metal is the reduction of the drift velocity of electrons due to collision with the lattice ions. If the temperature of the conductor is kept …