P2 and P3 - Mocks

L6(Extended) - IV Characteristics

In relation to a LDR, as light intensity increases, resistance decreases. In relation to thermistors, as temperature increases, resistance decreases.

To investigate the IV characteristics of a component we must set up a series circuit with a battery, a component that is to be investigated, a variable resistor, an ammeter in series and a voltmeter in parallel.

L7 - Series and Parallel Circuits

In a series circuit, current is equal at every point in the circuit. In a parallel circuit, the total current is the sum of the currents passing through each component.

In a series circuit, voltage us shared across components. In a parallel circuit, voltage is equal at every point in the circuit.

In a series circuit, adding more resistors will increase the total resistance. If more resistors are added in a parallel circuit, resistance decreases.

L9 - Mains Electricity

An alternating current is a current that switches direction at a given frequency. A direct current is bound by one direction.

The UK's mains electricity supply is a 50Hz, 230 Volts alternating current.

Within a plug, there are several components with individual purposes:

  • Earth Wire - [Green and Yellow] - Grounds the current through a 'low resistance' path if there is a fault in the device.
  • Neutral Wire - [Blue] - This wire simply completes the circuit.
  • Live Wire - [Brown] - This wire has 230 Volts applied over it and is dangerous because of this.
  • Fuse - This is a ceramic component that breaks the circuit if a fault causes too much current to flow.

L10 - Electrical Power

Power = Potential Difference x Current

Power = Current^2 x Resistance

The National Grid is a series of transformers and cables that 'distribute electricity' across the UK. A fuel station generates an high potential difference, step-up transformers increase this potential difference to maximise electrical power but reduce current as to avoid energy being lost as heat.

Step-down transformers decrease this potential difference so that it can be used domestically (230V).

L11 - Electrical Energy

Energy = Power x Time

Energy = Charge x Potential Difference

L 12 - Static Electricity

When electron are added or removed from an insulator, they become 'charged'. This creates a potential difference between the material and a grounded object (at 0V).

Electric field lines show the direction that a positive charge would go within the field (away from positive, towards negative).

L1 - Calculating Density

Density = Mass / Volume

To calculate the density of an irregular shape, use an electronic balance to find the mass of your object. Fill a Eureka can with water, slowly submerge the object in the Eureka can; the volume of the water displaced by the object is the object's volume.

L2 - Changing State

During a state change, the energy provided to a substance instead changes the potential store rather than the kinetic store.

L3 - Internal Energy

The internal energy of the particles is the sum of the kinetic energy they have due their individual motions relative to each other and the energy they have due to their individual positions relative to each other (sum of kinetic and potential).

L4 and L5 - Specific Heat Capacity and Specific Latent Heat

Energy Needed = Mass x Specific Heat Capacity x Change in Temperature.

Specific heat capacity is the energy needed to raise 1kg by 1 degree celsius.

Energy Needed = Mass x Specific Latent Heat

Specific latent heat is the energy needed to change the state of 1kg of a substance.