Significant figures rules: leading zeros are not significant; trailing zeros after decimal are significant. Thus 0.00250: leading zeros (before 2) not significant; digits 2,5,0 are significant (trailing zero after decimal counts). So three significant figures. Memory tip: 'Start counting at first non-zero digit; include trailing zeros after decimal'. This measurement precision concept is frequently tested in competitive exams. Always apply rules consistently: 0.0025 has two sig figs; 0.00250 has three, indicating higher precision.
Explanation:
Resistance depends on the resistivity of the material (R = ρL/A). Silver and copper are excellent conductors with very low resistivity. Aluminum is also a good conductor. Nichrome is an alloy (nickel, chromium, and often iron) with a resistivity about 60 times higher than that of copper, making it a resistor used in heating elements.
Explanation:
Doppler effect: observed frequency higher when approaching, lower when receding. Applications: radar speed guns, astronomical redshift/blueshift, echocardiography. Echo is reflection. Resonance is vibration matching. Diffraction is bending.
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