I/GCSE Physics Question Analysis Topic: Chapter 2: Electricity - Energy and Voltage in Circuits (Part 2)

For I/GCSE Physics, you should know:

Now, let's learn about the second part IGCSE Physics Chapter 2 sub-topic on "Energy and Voltage in Circuits."

Qualitative Effect of Changing Resistance on Current:

• As the resistance in a circuit increases, the current decreases.
• This is due to Ohm's law, which states that the current is inversely proportional to the resistance (I = V/R).
• So, if the resistance goes up, the current will go down, and vice versa.
  
  Variation of Resistance in Components:
• Light-Dependent Resistors (LDRs):
• The resistance of an LDR decreases as the illumination on the component increases.
• This makes LDRs useful for light-sensitive applications, such as automatic lighting controls.
• Thermistors:
• The resistance of a thermistor decreases as the temperature increases.
• Thermistors are used in temperature-sensing applications, such as in electronic devices to monitor and regulate temperature.
  
  Indicating the Presence of Current:
• Lamps and Light-Emitting Diodes (LEDs) can be used to indicate the presence of current in a circuit.
• When current flows through these components, they emit light, providing a visual indication of the circuit's operation.
  
  Relationship between Voltage, Current, and Resistance (Ohm's Law):
• Ohm's law states that the voltage (V) across a component is equal to the current (I) flowing through it multiplied by the resistance (R) of the component.
• The mathematical expression for Ohm's law is: V = I × R
  
  Current as the Rate of Flow of Charge:
• Current is the rate of flow of electric charge through a circuit.
• The unit of current is the ampere (A), which represents the flow of one coulomb of charge per second.
  
  Relationship between Charge, Current, and Time:
• The total charge (Q) that flows through a circuit is equal to the current (I) multiplied by the time (t) over which the current flows.
• The mathematical expression for this relationship is: Q = I × t

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