Physics for A/L

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05/05/2026

Ohm's Law defines the relationship between voltage (V), current (I), and resistance (R) in an electrical circuit, stating that current is directly proportional to voltage and inversely proportional to resistance (V = IR). It is fundamental to electronics, allowing calculation of one variable when the other two are known.

Key Takeaways:-

Proportionality: If voltage increases, current increases (if resistance is constant).

Inverse Relationship: If resistance increases, current decreases.

Application: Used to determine component values (resistors), analyze circuit behavior, and calculate power consumption.

Ohmic Materials: Materials that maintain constant resistance across varied voltages.

05/05/2026

The Doppler effect is the change in frequency or pitch of a wave (sound or light) produced by a moving source relative to an observer. When the source moves toward the observer, waves compress, resulting in higher frequency/pitch; when moving away, waves stretch, creating lower frequency/pitch. It applies to both sound and electromagnetic waves.

Key Aspects of the Doppler Effect:

Discovery: Described by Austrian physicist Christian Doppler in 1842.

Mechanism: It is the relative motion that matters. The effect increases with higher relative velocity.

Sound Examples: A passing ambulance siren, where the pitch drops sharply after passing.

Light Examples: Redshift and blueshift in astronomy, where stars moving away appear redder (lower frequency) and closer stars appear bluer (higher frequency).

Applications:

Medical: Doppler ultrasound (TCD) measures blood flow velocity through vessels.

Technology: Radar guns used by police, weather monitoring, and navigation systems.