Physics GCSE, Questions & Answers

Physics GCSE, Questions & Answers +325 V and -325 V (equivalent to a direct current of 230 V) - CORRECT ANSWER- What peaks/troughs does the live wire alternate between and what is the equivalent of a direct current? 0 volts - CORRECT ANSWER- What voltage does the neutral wire supply? 1) Attach one end of a string to an oscillator attached to a frequency generator and the other end to a pulley with a weight 2) Before turning the oscillator on, measure the length of the string 3) Turn the oscillator on and find the frequency which gives the fundamental frequency or third harmonic 4) If there's a fundamental frequency (one loop), the length is equal to half the wavelength. If there's a 2nd harmonic (2 loops) the length is equal to the wavelength. Remember that each loop is half a wavelength 5) find the wavespeed - CORRECT ANSWER- How can you investigate waves on a string using a frequency generator and oscillator? 1)Attach a toy car to a piece of string with is looped around a pulley with a 1 N weight attached. Draw chalk lines on the desk every 10 cm 2)Let go of car from starting point and start timer - record this with a phone so it can be slowed down. Measure the time at which it passes through each 10 cm marker 3)Repeat several times with a decreased weight Alternatively, repeat with a constant weight on string but add a 200 g mass to car and record times. Repeat and increase mass added to car. - CORRECT ANSWER- How would you do a practical for acceleration? 1)Attach one end of a string to a vibration generator and the other to a wooden bridge and a pulley with a hanging mass 2)Turn on power and use signal generator to change frequency until you get the 2nd harmonic (1 wave - two loops of string) 3)Measure the length of the string from the wooden bridge to the vibration generator 4)Multiply this by the frequency to find the wave speed 5)For each harmonic, divide the harmonic by 2 and divide the length of the string by that to find the wavelength - CORRECT ANSWER- How would you do a practical for waves in a solid? 1)Circuit with a battery, ammeter, wire (independent variable could be length or thickness), and a switch. A voltmeter should be in parallel with the wire 2)Attach wire to a ruler with tape and connect it to circuit with crocodile clips. This makes it easy to change the length 3)Take readings from the voltmeter and ammeter to find the resistance. Repeat this with several different lengths of wire 4)Sources of error: Zero error - measuring instrument gives a value when it should be zero since resistance is caused by contact between crocodile clip and wire. Temperature increases resistance - use low p.d. and turn off current between readings 5)Length and resistance are directly proportional - CORRECT ANSWER- How would you do a practical for the effect of the length of a wire on resistance? 1)Clouds of dust and gas are pulled together by gravity to form a protostar 2)The protostar becomes denser and the nuclei of hydrogen and other light elements start to fuse together, releasing energy 3)The stare radiates energy because of hydrogen fusion in its core - this process continues until it runs out of hydrogen nuclei (billions of years). The star is stable because the inward force of gravity and the outward force of radiation balance - this is a main sequency star 4)Depending on the size of the star, it will become a red giant or red supergiant when it runs out