- (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. [2]
(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. [2]
(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.
(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. [3]
(iii) The magnitude of B is 2.5 T. Calculate the frequency of revolution of the proton. [1]