- (a) The diagram shows a junction in a circuit.
The currents in the three wires are related by I₁ = I₂ + I₃. State the fundamental law of Physics from which this relation is derived. [1]
(b) A cell of emf 1.50 V and internal resistance r is connected to a resistor of resistance 5.00 Ω and an ideal voltmeter V. The reading of the voltmeter is 1.20 V.
(i) Determine the internal resistance r of the cell. [1]
(ii) A second 5.00 Ω resistor is connected in parallel to the first resistor.
State and explain the change, if any, in the voltmeter reading without further calculation. [1]
(c) A proton moves on a circular path in a region of uniform magnetic field of magnetic flux density B that is directed into the plane of the page.
diagram of proton in circular path within magnetic field
(i) On the diagram, draw an arrow to indicate the velocity of the proton at the position shown. [1]
(ii) Show that the frequency of revolution of the proton is given by f = eB / (2πmₚ). [2]
(iii) The magnitude of B is 2.5 T. Calculate the frequency of revolution of the proton. [1]