Physics Past Paper - Amjad School, 1st Secondary - Generator

Amjad School Date: Subject: Physics Class: 1st Secondary Name:.................

Amjad School Date: Subject: Physics Class: 1st Secondary Name:.................... Extra sheet (Generator) Chapter: 5 Characteristics of a generator Objectives: 1- Know that the voltage at the terminals of a generator depends on the intensity of the current it delivers; 2- Know how to draw the curve representing the variation of the voltage across the terminals of a generator as a function of current (U-I characteristics); 3- Know that a generator is characterized by its emf (E) and its internal resistance (r). Experimental approach 1) Using a battery, a lamp, two multimeters, a switch and the connection wires, draw the circuit that enables us to measure the voltage across the battery and the current through it. 2) Add lamps in parallel and record the indication (U) of the voltmeter across the terminals of the generator for each value of the current (I) measured by the ammeter. Write these results in the table below: U (V) I (mA) 3 Answer the following questions 3.1) Does the voltage (U) across the terminals of the generator remain constant as the current varies?......................................................................................................................................................... 3.2) Indicate how (U) varies as a function of (I)................................................................................... 4) Draw the curve representing the variation of (U) as a function of (I). Scale: I axis: 1cm ↔....... A U axis: 1cm ↔....... V 5) Indicate the shape of the characteristic curve...................................................................................... …………………………………………………………………………………………………………. 6) The equation of the graph U= f(I) has the form: U= aI + b where a and b are two constants. 6.1) Determine (b) and indicate its unit in (SI)................................................................................................................................................................................................................................................ 6.2) The constant (b) represents the electromotive force emf (E) of the generator. Give the physical meaning of (E)................................................................................................. …………………………………………………………………………………………………….. Is (E) constant or it varies with the current I ?.................................................................................. Measure, for other two non-load batteries marked 1.5V and 9V, the voltage across their terminals. Would they have the same value of (E) ?........................................................................................................................................................ Can we say that (E) is a characteristic of a generator?.................................................................. 7) 7.1) Determine (a) and indicate its unit in (SI)......................................................................................... 7.2) Based on the unit of (a), what does (a) represent?...................................................................... 7.3) Does a generator have its own internal resistance?.............................................................. Write the general form of the voltage (U) across a generator (E, r) in terms of the current (I). …………………………………………………………………………………………………………..