3.5.1.1a Basics of electricity
Qs MS EN
Name:
________________________
Class:
________________________
Date:
________________________
Time:
363 minutes
Marks:
260 marks
Comments:
ASA
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3.5.1.1a Basics of electricity
Qs MS EN
Name: ________________________
Class: ________________________
Date: ________________________
Time: 363 minutes
Marks: 260 marks
Comments: ASA
A cell with negligible internal resistance is connected to two resistors of resistance 4 R and R. The currents I 1 , I 2 and I 3 in the circuit are shown. 1. Which equation is correct for this circuit? A (^) I 1 = 4 I 2 B (^) I 1 = 4 I 3 C (^) I 2 = 4 I 3 D (^) I 3 = 4 I 1 (Total 1 mark) The current in a resistor is 15 mA. How many electrons pass through the resistor in 3 minutes? A (^) 2.8 × 1017 B (^) 1.7 × 1019 C (^) 2.8 × 1020 D (^) 1.7 × 1022 (Total 1 mark) 2.
(b) Figure 3 shows the variation of current with voltage for the lamp between 2 V and 12 V. Figure 3 Calculate the resistance of the lamp when the voltage across the lamp is 8.0 V. resistance = _______________ Ω (2) (c) Explain, in terms of electron movement, why the resistance of the filament lamp changes as the voltage changes as shown in Figure 3.
(3)
(d) Figure 4 shows an alternative circuit used to investigate the variation of current with voltage for the lamp. Figure 4 The circuit components are the same as in Figure 2. When the voltage across the lamp is 12 V its resistance is 6.0 Ω. P is moved to position Y. Calculate the total resistance of the circuit. total resistance = _______________ Ω (2) (e) Calculate the power transferred by the battery when P is at position Y. power = _______________ W (2)
A student buys a portable loudspeaker that is powered by its own internal battery. The battery in the loudspeaker is initially uncharged. (a) The battery is connected to a charger that maintains a constant potential difference of 5.0 V across the battery. It takes 2.6 hours for the battery to become fully charged. The average current in the battery during this time is 2.0 A. The battery is disconnected from the charger. The fully-charged battery operates the loudspeaker for 12 hours before it is completely discharged. Calculate the average output power of the battery during these 12 hours. average output power = _______________ W (2) 4. (b) A mobile phone transmits data to the loudspeaker using microwaves. The data are processed at the loudspeaker to produce sound waves. Microwaves and sound waves travel at different speeds. Describe two other differences between microwaves and sound waves. 1 _________________________________________________________________
2 _________________________________________________________________
(2)
(c) A second loudspeaker receives the same data from the mobile phone. The two loudspeakers act as coherent sources of sound waves. State the two conditions required for the sources to be coherent. 1 _________________________________________________________________
2 _________________________________________________________________
(2) The figure below shows two loudspeakers A and B that act as coherent point sources of sound of a single frequency. C is the midpoint between A and B. Distances OA and OB are equal. OP is perpendicular to CO. The student uses a sound-level meter to measure the intensity of the sound. The meter detects a maximum intensity at O. The student moves the meter along OP. The intensity decreases and reaches a first minimum at M. The intensity then increases as the meter moves towards P. The student records the following distances: AB = 1.80 m CO = 8.00 m OM = 1.24 m.
The currents in the four wires obey the relationship I 1 + I 2 + I 3 + I 4 = 0 This relationship is an expression of the law of conservation of A charge. B energy. C potential difference. D power. (Total 1 mark) 5. The current in a metallic conductor is 1.5 mA. How many electrons pass a point in the conductor in two minutes? A (^) 1.1 × 1018 B (^) 1.9 × 1019 C (^) 1.4 × 1020 D (^) 2.0 × 1029 (Total 1 mark) 6.
(a) A light emitting diode (LED) emits blue light with a wavelength of 440 nm. The rate of photon emission is 3.0 × 1016 s−1. Show that the power output of the LED is approximately 0.014 W. (2) 7.
(c) The student has paint that fluoresces when light of any wavelength is incident on it. She coats the blue LED and the red LED with the paint. Compare the wavelengths of light emitted by the paint on each LED. In your answer you should also explain the processes that cause the paint to fluoresce.
(6) (Total 11 marks) Measurements are taken to determine the resistivity of a uniform metal wire. The table shows the quantities measured and their percentage uncertainties. Quantity Percentage uncertainty potential difference across wire 0.3% current in wire 5.0% diameter of wire 4.0% length of wire 0.2% 8.
What is the percentage uncertainty in the calculated value for the resistivity of the metal of the wire? A 1.6% B 9.5% C 13.5% D 21.5% (Total 1 mark) Scintillation counters are used to detect beta particles. A scintillation counter consists of a scintillation material and a photomultiplier tube (PMT). (a) Beta particles collide with atoms in the scintillation material, which emits photons of light as a result. Explain how photons are produced by collisions between beta particles and atoms.
(2) 9. (b) A photon of light from the scintillation material enters the PMT, as shown in Figure 1. The front of the PMT contains a thin photocathode. The photon strikes the photocathode to release an electron. Figure 1
The electrodes, anode and photocathode are connected to a potential divider consisting of four identical resistors R. The emf of the electrical supply is 3.0 kV. The potential difference between the photocathode and the first electrode accelerates the electron along the path shown in Figure 2. Calculate, in J, the maximum kinetic energy transferred to the electron when it accelerates from the photocathode to the first electrode. maximum kinetic energy = _______________ J (2) (d) The electron hits the first electrode and causes the release of several electrons. Figure 3 shows how a series of accelerations and collisions produces a large number of electrons. These electrons hit the anode and produce a pulse of current in an ammeter. Figure 3
The Figure 4 shows the variation of current in the ammeter with time due to this pulse. Figure 4 Determine the number of electrons that flow through the ammeter. number of electrons = _______________ (4) (Total 10 marks)
Figure 2 shows how the current in the motor’s circuit varies with time. Figure 2 (a) Determine the total energy input by the 24 V battery to the motor in the first 200 ms. total energy input = ____________________ J (3)
(b) The boat and trailer are initially at rest. In the first 200 ms the boat and trailer are raised through a vertical height of 3.3 × 10 –2^ m and the speed increases to 0.85 m s–1. Assume that all the useful energy output by the motor is transferred into kinetic energy and gravitational potential energy of the boat and trailer. The boat and trailer have a total mass of 180 kg. Determine the average efficiency of the motor during these first 200 ms. average efficiency = ____________________ (3) (c) Either of the circuits shown in Figure 3a and Figure 3b could be used to reduce the initial current surge. Figure 3a Figure 3b The thermistor and the fixed resistor have the same resistance when they are at the temperature of the surroundings. When the surge has ended, the boat and trailer continue to move at a constant speed to the top of the ramp.