Topic 5 covers electric circuits, including DC circuit analysis, and introduces magnetic fields and their interaction with moving charges and current-carrying conductors.
Current I = ΔQ/Δt (A). Potential difference V = W/Q (V). Resistance R = V/I (Ω). Ohm\'s law: V ∝ I for ohmic conductors. Series: R_total = R₁ + R₂. Parallel: 1/R_total = 1/R₁ + 1/R₂. Kirchhoff\'s first law: ΣI_in = ΣI_out (charge conservation). Second law: ΣV = 0 around any closed loop (energy conservation).
EMF (ε) is the energy per unit charge supplied by the source. Terminal voltage: V = ε − Ir where r is internal resistance. For a complete circuit: ε = IR + Ir. Power dissipated: P = IV = I²R = V²/R. Efficiency of energy transfer depends on load resistance relative to internal resistance.
Magnetic field B (tesla). Force on a moving charge: F = qvBsinθ (direction by right-hand rule or Fleming\'s left-hand rule). Force on a current-carrying wire: F = BILsinθ. Circular motion of charged particles in uniform B: r = mv/(qB). Applications: mass spectrometer, velocity selector.
Magnetic flux: Φ = BAcosθ (Wb). Faraday\'s law: EMF = −ΔΦ/Δt (or −NΔΦ/Δt for N turns). Lenz\'s law: induced current opposes the change producing it (hence the minus sign). Applications: generators (rotating coil in magnetic field), transformers (Vp/Vs = Np/Ns), and eddy currents.
EMF (electromotive force) is the energy per unit charge supplied by a source (battery, generator) — it is the total voltage the source provides. Potential difference (PD) is the energy per unit charge transferred to a component. They differ because of internal resistance: V_terminal = EMF − Ir. When no current flows, terminal PD equals EMF. EMF is a property of the source; PD is measured across a component.
Book a Trial + Diagnostic session. Get a personalized Learning Path with clear milestones, tutor match, and a plan recommendation — all within 24 hours.
Book Trial + Diagnostic →