The trace moves up or down but keeps exactly the same shape. The trace becomes more spread out horizontally. For example, a trace that previously covered 3.4 divisions along the will now cover 6.8 divisions. x-axis The whole trace moves to the left or right but keeps exactly the same shape. Use Y-shift to move the trace to the middle of the screen. Rotate Y-input anticlockwise so making the trace of larger height on the screen. Rotate timebase anticlockwise so making the trace of larger width on the screen. Not all oscillations are sinusoidal! (a) They are both of the same height. 2 V (a) The time for one wave as measured by the distance along the is different for x-axis the two square waves. One complete wave takes 20 ms, so frequency = = = 50 Hz (This is mains frequency.) (a) In trace 1 the variation of voltage squared varies at twice the frequency of the input signal. For mathematicians, if the input signal is = sin (2ft) V V0 then 2 = sin2 (2ft) = V V02 V02 Mean value of voltage squared over a full cycle: trace 1 halfway up the 2 graph (by symmetry) = 2 V V trace 2 halfway up the 2 graph (by symmetry) = 2 V V trace 3 constant value of 2 = 4 V V For trace 1: = = =V Vrms or the square root of average value of 2 =V V For trace 2: square root of average value of 2 =V V For trace 3: square root of average value of 2 = 2 V V The value of 2 is constant and thus the heating effect is constant. V Alternatively, in trace 3 the voltage is either +4 V or V. The current in a heater −4 will be either one way or the other but will be constant in value. The direction of the current does not affect the amount of heat produced.
The trace moves up or down but keeps exactly the same shape. The trace becomes more spread out horizontally. For example, a trace that previously covered 3.4 divisions along the x-axis will now cover 6.8 divisions. The whole trace moves to the left or right but keeps exactly the same shape. Use Y-shift to move the trace to the middle of the screen. Rotate Y-input anticlockwise so making the trace of larger height on the screen. Rotate timebase anticlockwise so making the trace of larger width on the screen. Not all oscillations are sinusoidal! (a) They are both of the same height. 2 V (a) The time for one wave as measured by the distance along the x-axis is different for the two square waves. One complete wave takes 20 ms, so frequency = = = 50 Hz (This is mains frequency.) (a) In trace 1 the variation of voltage squared varies at twice the frequency of the input signal. For mathematicians, if the input signal is V = V0 sin (2ft) then V 2 = V02 sin2 (2ft) = V02 Mean value of voltage squared over a full cycle: trace 1 halfway up the V 2 graph (by symmetry) = 2 V trace 2 halfway up the V 2 graph (by symmetry) = 2 V trace 3 constant value of V 2 = 4 V For trace 1: Vrms = = =V or the square root of average value of V 2 =V For trace 2: square root of average value of V 2 =V For trace 3: square root of average value of V 2 = 2 V The value of V 2 is constant and thus the heating effect is constant. Alternatively, in trace 3 the voltage is either +4 V or −4 V. The current in a heater will be either one way or the other but will be constant in value. The direction of the current does not affect the amount of heat produced.