Electricity

• Current (I)= charge (Q) / time (s)
• Ammeter measures current
• The ammeter is connected in series in the circuit, which means inside the circuit
• Potential difference is measured by a voltmeter
• Voltage= current x resistance (V=IR)
• Resistance is measured in ohms (Ω)
• Ohm’s law states that current and potential difference in a conductor are directly proportional if the temperature stays constant.
• Resistance is created when electrons collide with metal ions. When they collide, the electrons give little energy to the ions. Ions with more energy vibrate more, increasing the chance of a collision with an electron. This increases the resistance.
• Diodes are components that allow current to flow in one direction only. They can also be used to prevent damage to a circuit from current flowing in the wrong direction.
• A series circuit is when all components are connected on the same loop of wire.
• A parallel circuit has two or more loops. Current and voltage are shared between the loops or branches.
• In a series circuit, current stays the same all the way around. However, voltage is shared between components.
• A light dependant resistor (LDR) is a resistor whose resistance depends on how much light falls on it.
• In an LDR, resistance decreases as light intensity increases.
• A thermal resistor (aka a thermistor) has resistance that is dependant upon temperature.
• In a thermistor, resistance decreases as temperature increases.
• There are two types of change:

  Positive charge

  Negative charge
• Similar charges repel and opposite charges attract.
• A material that gains electrons becomes negatively charged. A material that loses electrons becomes positively charged.
• In electricity, the charge carriers are usually negative electrons. Rubbing some materials together transfers negative electrons to one surface.
• Charge (C)= current (A) x time (s)
• Potential difference is the energy transferred to a circuit or a component. 1 volt= 1 joule of energy transferred per coulomb.
• Potential difference (V)= energy transferred (J) / charge (C)
• If the resistance in a circuit is increased, there are more electron collisions.
• A longer wire in a circuit= higher resistance

  A thinner wire in a circuit= higher resistance
• Current is the flow of electrons. Moving electrons collide with ions in the metal. Electron flow is slowed by this and they give up a lot of energy doing this too.
• A diode needs to flow from positive to negative.
• Resistance in a series circuit can be added together to find the total resistance.
• In a parallel circuit, current is shared between branches. Voltage is the same.
• A parallel circuit has more than one ‘loop’.

  A series circuit has only one ‘loop’.
• Zero error is when an apparatus gives a false reading. For example, if an ammeter is showing a reading even when it is turned off.
• When diodes are put in reverse, they have high resistance so current cannot pass through.
• What component is this graph showing?

  Bulb

  
• What component is this graph showing?

  Resistor

  
• What component is this graph showing?

  Diode.

  
• What type of resistor is this graph showing?

  Light dependant resistor (LDR)

  
• What type of resistor is this graph showing?

  Thermal resistor (thermistor)

  
• Direct current (D.C) is current that flows in only one direction.
• Alternating current (A.C) is current that changes directions multiple times a second.
• What current is flowing through graph A?

  Direct current.