Eduqas A Level Physics Component 2: Electricity and the Universe Exam Questions

About Eduqas A Level Physics Component 2: Electricity and the Universe

Component 2 of Eduqas A Level Physics, Electricity and the Universe, combines electrical physics with astrophysics. It covers drift velocity and resistivity, potential dividers and internal resistance, capacitor charging and discharging, the behaviour of solids under stress, electric and gravitational fields, the use of radiation to study stars, and orbits, including dark matter and Hubble's law. Field ideas link back to energy in Component 1 and forward to magnetism in Component 3. Examiners often set exponential decay calculations for capacitors, Young modulus and stress-strain graph questions, field and potential comparisons, and black body radiation problems using Wien's and Stefan's laws.

What you need to know

• 2.1 and 2.2 Current as rate of flow of charge, I = nAve, potential difference as energy per unit charge, Ohm's law, I-V characteristics, resistivity R = rho L / A, and the effect of temperature on resistance including superconductivity.
• 2.3 Kirchhoff's laws, series and parallel resistors, potential dividers with thermistors and LDRs, and EMF and internal resistance V = E - Ir.
• 2.4 Capacitance C = Q / V, parallel plate capacitors C = epsilon0 A / d, energy stored 1/2 QV, and exponential charge and discharge with time constant RC.
• 2.5 Hooke's law, stress, strain and the Young modulus, elastic and plastic deformation, and the behaviour of metals, polymers and brittle materials.
• 2.6 Coulomb's law and Newton's law of gravitation as inverse square laws, field strength, potential, equipotentials, and similarities and differences between electric and gravitational fields.
• 2.7 Black body spectra, Wien's law lambda max T = 2.90 x 10^-3 m K, Stefan's law P = A sigma T^4, absorption line spectra and the multiwavelength study of stars.
• 2.8 Kepler's laws, circular orbits and T^2 proportional to r^3, Doppler shift to detect exoplanets and binary stars, galaxy rotation curves and dark matter, and Hubble's law v = H0 d.

Common mistakes in Component 2: Electricity and the Universe

• Saying current is used up around a circuit. Charge is conserved, so current is the same at every point in a series circuit; energy is transferred, not current.
• Confusing the time constant with the time to fully discharge. After one time constant RC the charge falls to about 37% of its initial value.
• Using radius from the surface in gravitational field calculations. Distances are measured from the centre of the mass.
• Using the wrong temperature in Wien's law. The temperature must be in kelvin, and lambda max is the peak wavelength, not the shortest.
• Treating electric potential as always positive. Gravitational potential is always negative, and electric potential near a negative charge is also negative.

Try three Component 2: Electricity and the Universe exam-style questions