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Overview

Think Like a Scientist

January 15, 2025
2 min read
practice critical-thinking

Scenario 1: The Weak Electromagnet

Problem: You built an electromagnet using a single cell and 20 turns of wire, but it can barely pick up one paper clip. How can you make it stronger without changing the battery?

Solution: You can increase the magnetic strength by:

  1. Increasing the number of turns: Wrap more wire around the nail (e.g., 50 or 100 turns).
  2. Changing the Core: Ensure you are using a soft iron nail (steel retains magnetism but isn’t as strong instantly).
  3. Tighter Windings: Ensure the coils are packed closely together.

Scenario 2: The Hot Wire Mystery

Problem: You have two Nichrome wires of the same length. Wire A is thin, and Wire B is thick. You connect them to the same battery one by one. Which one will generate more heat?

Analysis:

  1. Resistance: Thinner wire (A) has higher resistance than thicker wire (B).
  2. Heat: generally, higher resistance generates more heat potential, but high resistance also reduces current flow.
    • Actually, this is complex! Heat =I2Rt= I^2Rt.
    • If connected to the same voltage (battery): Heat=V2/RHeat = V^2/R.
    • Since Resistance is in the denominator, a Lower Resistance (Thick wire) draws much more current.
    • Result: The Thick Wire (B) might actually get hotter or glow brighter because it draws significantly more power (P=VIP=VI) from the battery, assuming the battery can supply it!
    • Textbook Context: Usually, textbooks emphasize “High Resistance = Heat”. If the current was kept constant (series circuit), the Thin wire would heat more. But with a fixed Voltage source (parallel/single), the Thick wire draws more power.
Note

Simplified Grade 8 View: In your activities, you learned Nichrome (High R) heats up while Copper (Low R) doesn’t. This suggests high resistance leads to visible heating. So, typically, you would expect the Thin Wire to glow red hot more easily because the heat is concentrated in a smaller mass, even if total power is lower.

Scenario 3: Lemon Battery Challenge

Problem: You made a lemon battery but the LED isn’t glowing. List three possible reasons.

Troubleshooting:

  1. Same Metals: Did you use two copper strips? You need Copper (+) and Zinc/Iron (-).
  2. Dry Lemon: The lemon might not be juicy enough (poor electrolyte). Roll it to break internal sacs.
  3. LED Polarity: LED only works one way. Try flipping the legs (Long leg to Copper).
  4. Voltage too low: One lemon provides ~0.9V. An LED needs ~2-3V. You might need 3-4 lemons in series.