Physics - electricity

• What is a fixed resistor?

  A resistor limits the flow of current. A fixed resistor has a resistance that cannot change.

  
• What is a variable resistor?

  A resistor with a slider that can be used to change its resistance. These are often used in dimmer switches and volume controls.

  
• What is a thermistor?

  The resistance of a thermistor depends on its temperature. As its temperature increases, its resistance decreases.

  
• What is a light-dependent resistor (LDR)?

  The resistance of the LDR depends on light intensity. As the light intensity increases, its resistance decreases.

  
• What is a diode?


  A diode allows current to flow in one direction only. They are used to convert AC to DC current.

  
• What is a light-emitting diode (LED)?

  This is equivalent to a diode and emits light when a current passes through it. These are used for aviating lighting and displays (TVs, road signs)

  
• What is an ammeter?

  Used to measure current in a circuit. Connected in series with other components.

  
• What is a voltmeter?

  Used to measure the potential difference of an electrical component. Connected in parallel with relevant components.

  
• What is a cell/battery?

  Provides the circuit with a source of potential difference. A battery is two or more cells.

  
• What is potential difference?

  The energy transferred per unit charge flowing from one point to another.
• What is energy transferred also called as?

  Work done
• What is the equation for potential difference?

  Potential difference (V) = Work done (J) ÷ charge (C)

  
• What is an electric current?

  The flow of electrical charge
• What is an electric current measured in?

  Amperes (A) or amps
• What is the symbol of current?

  I
• What is the size of the electric current?

  The size of the electric current is the rate of flow of electrical charge.
• What is the electrical charge that flows in metals?

  The electrical charge that flows is delocalised electrons. So the current in a circuit is a flow of electrons.
• What is the equation for charge?

  Charge (C) = current (A) x time (s)

  
• What is the unit for charge?

  Coulomb (C)
• Where do electrons flow in current?

  They flow away from the negative terminal of a cell towards the positive terminal. This is because electrons are negatively charged.
• What is conventional current?

  The flow of positive charge from the positive terminal of a cell to the negative terminal.
• Why is conventional current opposite to the direction of electron flow?

  Conventional current was being put to use before the discovery of the electrons.
• What is used to measure current?

  Ammeter
• Why is the current the same value at any point in series?

  The number of electrons per second that passes through one part of the circuit is the same number that passes through any other part.
• Why is resistance defines as the opposition to current?

  The higher the resistance of a circuit, the lower the current.
• What is the symbol for resistance? What is it measured in?

  The symbol is R. It's measured in Ohms,Ω

  
• What is an Ohm defines as?

  One volt per ampere
• What does the current through a component depend on?

  The resistance of the component and the potential difference across the component.
• What is the equation for potential difference (voltage)?

  Potential difference (V) = Current (A) × Resistance (Ω)