4.4.1. Uses of electricity
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 84 questions
shows a solar-powered charger connected to a cell phone (mobile phone). cell phone solar-powered charger The battery inside the cell phone is charged by the solar-powered charger. Complete to show the useful transfer of energy from the Sun to the battery. energy in Sun light from Sun electrical current energy in battery electric field in charger Explain why the battery takes a long time to charge on a cloudy day. After use, the outside surface of the cell phone is warm. When switched off, the cell phone cools down. Name and describe the three processes by which thermal energy is transferred as the cell phone cools down. It takes 4.5 hours to charge the battery with an average current of 300 mA. Calculate the quantity of charge that enters the battery. Give the unit of your answer. charge = unit
5054_s24_qp_22
THEORY
2024
Paper 2, Variant 2
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shows a device used to generate electricity. Water entering at the top turns the wheel. A generator connected to the wheel produces electric current. State the two main energy changes that take place in this device as water starts to flow. 1. 2. The change in the potential energy of the water every second is 2000 J. The electrical energy output is 1200 J every second. Calculate the efficiency of the process. efficiency = State two ways in which the device wastes energy. 1. 2. water out water in generator wheel Use
5054_w06_qp_2
THEORY
2006
Paper 2, Variant 0
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A thin metal filament J and a metal plate K are sealed inside an evacuated glass vessel. The electrical connections pass through the glass to external components as shown in . mA 6.0 V battery K S J evacuated glass vessel 1.5 kV d.c. power supply + – A 6.0 V battery is connected to J and the filament becomes white hot. The current from the battery is 1.6 A. Calculate the power supplied by the battery. A milliammeter and a 1.5 kV d.c. power supply are connected in series between K and J. The positive terminal of the power supply is connected to K. The milliammeter registers a small current. Explain the presence of a current in this circuit despite the gap between J and K. State why the glass vessel must be evacuated. One pole of a bar magnet is brought close to the side S of the glass vessel and the current registered by the milliammeter decreases. Explain why this happens. The terminals of the 1.5 kV d.c. power supply are reversed. Explain how this affects the current in the milliammeter. Question 11 is continued on page 13. shows two terminals M and N of a potential divider connected to a 6.0 V battery. N is also connected to one of the two Y-input terminals of a cathode-ray oscilloscope. The other Y-input terminal is connected to the sliding contact of the potential divider . 6.0 V M N cathode-ray oscilloscope one division The sliding contact is at N and the trace on the oscilloscope is a horizontal line passing through the centre of the screen. The timebase setting is 1.0 ms / div. Explain why the trace is a horizontal line. The Y-gain setting is 2.0 V / div. The sliding contact is moved at a slow, uniform rate from N to M. Describe in detail what happens to the trace on the screen. The Y-gain setting is now changed to 1.0 V / div and the trace disappears from the screen. State why this happens.
5054_w08_qp_2
THEORY
2008
Paper 2, Variant 0
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Questions Discovered
84