10.1. Practical circuits
A subsection of Physics, 9702, through 10. D.C. circuits
Listing 10 of 112 questions
shows the circuit diagram containing an operational amplifier (op-amp). – + + 3.0 V 3.6 kΩ 0.72 kΩ VOUT VIN – 3.0 V State the name of this type of amplifier. Show that the gain of the amplifier is 6.0. At time t = 0 the input potential VIN is zero. VIN then gradually increases with time t as shown in . T t potential / V On sketch a line to show the variation with time t of the output potential VOUT from time t = 0 to time t = T. State how the circuit of may be changed so that the gain of the amplifier is dependent on light intensity. An op-amp is to be used to switch on a high-voltage heater. State the name of the component used as the output device of the op-amp. Complete using the device named in and a diode so that the heater may be switched on when the output of the op-amp is positive. – connections to high-voltage heater + – +
9702_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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10 State the name of an electrical sensing device that will respond to changes in length, pressure. A relay is sometimes used as the output of a sensing circuit. The output of a particular sensing circuit is either + 2 V or – 2 V. On , draw symbols for a relay and any other necessary component so that the external circuit is switched on only when the output from the sensing circuit is + 2 V. terminals of external circuit output from sensing circuit +2 V or –2 V
9702_s10_qp_42
THEORY
2010
Paper 4, Variant 2
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10 State the name of an electrical sensing device that will respond to changes in length, pressure. A relay is sometimes used as the output of a sensing circuit. The output of a particular sensing circuit is either + 2 V or – 2 V. On , draw symbols for a relay and any other necessary component so that the external circuit is switched on only when the output from the sensing circuit is + 2 V. terminals of external circuit output from sensing circuit +2 V or –2 V
9702_s10_qp_43
THEORY
2010
Paper 4, Variant 3
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A student designs an electronic sensor that is to be used to switch on a lamp when the light intensity is low. Part of the circuit is shown in . +5 V + – 240 V sensing device output device processing unit –5 V X +5 V State the name of the component labelled X on . On , draw the symbols for two resistors to complete the circuit for the sensing device, a relay to complete the circuit for the processing unit. State the purpose of the relay. Suggest why the diode is connected to the output of the operational amplifier (op-amp) in the direction shown.
9702_s12_qp_41
THEORY
2012
Paper 4, Variant 1
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A student designs an electronic sensor that is to be used to switch on a lamp when the light intensity is low. Part of the circuit is shown in . +5 V + – 240 V sensing device output device processing unit –5 V X +5 V State the name of the component labelled X on . On , draw the symbols for two resistors to complete the circuit for the sensing device, a relay to complete the circuit for the processing unit. State the purpose of the relay. Suggest why the diode is connected to the output of the operational amplifier (op-amp) in the direction shown.
9702_s12_qp_43
THEORY
2012
Paper 4, Variant 3
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The circuit of an inverting amplifier incorporating an ideal operational amplifier (op-amp) is shown in . V IN R2 R1 V OUT +V –V + – P Explain why point P is known as a virtual earth. Derive an expression, in terms of the resistances R1 and R2, for the gain of the amplifier circuit. Explain your working. A relay and the output terminals of the amplifier circuit are shown in . V OUT On , show how the relay may be connected to the amplifier output so that the relay operates only when VOUT is positive.
9702_s16_qp_41
THEORY
2016
Paper 4, Variant 1
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Questions Discovered
112