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Required Practicals (Resistance (of a wire) (An electric current flows…
Required Practicals
Resistance (of a wire)
The resistance in a wire increases as:
The length of the wire increases
The thickness of the wire decreases
Resistance is measured in ohms. It can be calculated from the potential difference across a component and the current flowing through it. The total resistance of a series circuit is the sum of the resistances of the components in the circuit.
An electric current flows when electrons move through a conductor, such as a metal wire. The moving electrons can collide with the ions in the metal. This makes it more difficult for the current to flow, and causes resistance.
The resistance of a long wire is greater than the resistance of a short wire because electrons collide with ions more often.
The resistance of a thin wire is greater than the resistance of a thick wire because a thin wire has fewer electrons to carry the current.
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Electrolysis
Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them.
For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted
Electricity is the flow of electrons or ions. For electrolysis to work, the compound must contain ions. Covalent compounds cannot act as electrolytes because they contain neutral atoms.
Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.
Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.
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Specific Heat Capacity
temperature - measure of how hot something is
heat - measure of the thermal energy contained in an object.
The specific heat capacity of a substance is the amount of energy needed to change the temperature of 1 kg of the substance by 1°C. Different substances have different specific heat capacities. The table shows some examples.
E = m × c × θ
E is the energy transferred in joules, J
m is the mass of the substances in kg
c is the specific heat capacity in J / kg °C
θ (‘theta’) is the temperature change in degrees Celsius, °C
