Figure 1 represents a circuit diagram. Use it to answer the questions that follow. (a) Name the parts labelled P, Q and R. (b) State Ohm's Law.

• P is a variable resistor, also known as a rheostat.

• Q is an ammeter, used to measure current.

• R is a cell or battery, which provides the electromotive force.

• P: Variable resistor (or Rheostat)

• Q: Ammeter

• R: Cell (or Battery)

(b) State Ohm's Law.

Ohm's Law describes the relationship between voltage, current, and resistance in an electrical circuit.

• Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them, provided the temperature and other physical conditions remain constant.
• Mathematically, it is expressed as $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.

8. (a) Name two excretory organs in plants and animals.

Excretory organs remove waste products from an organism.

• (i) plants:
  • Stomata (for gaseous waste like oxygen and water vapor)
  • Lenticels (for gaseous waste)
  • Leaves (for storing waste that is shed during leaf fall)
• (ii) animals:
  • Kidneys (for filtering blood and producing urine)
  • Lungs (for expelling carbon dioxide and water vapor)
  • Skin (for sweating out water, salts, and urea)

(b) Name two materials that can be attracted by a magnet.

Ferromagnetic materials are strongly attracted to magnets.

• 1. Iron
• 2. Nickel
• 3. Cobalt