(a) 80 W 50 V If a occurs, the current 85 W 40 V can get much higher than is 45 000 J safe (up to 13 A). This can 1 305 000 J 759 W cause dangerous 250 s overheating of the flex. 140 s 3.5 A The fuse will blow as the 90 W 12 V current is greater than 3 A. 62 640 000 J 0.52 A The current is above 3A when the vacuum is turned 600 s 110 V (approximately) on although the current drops below 3A when it is (a) 748 800 J in normal operation. More 28 800 J current is required to start Standby = 138 240 J the motor. Full Power = 140 400 J Full for 45 minutes 3 A fuse (I = 0.87 A) uses up more energy. 10 A fuse ( I = 5.2 A) (a) 306 000 J 2.5 hours 13 A fuse (I = 10.9 A) 158 400 25 200 – = 133 200 J 5A fuse (I = 4.35 A) 1300 W Power & Resistance (p54 57) – Power, Current & Voltage Fuses (p53) (p51 52) P = I V – The fuse protects the P = I x IR flex (a) 1.35 W of an appliance from P = I2 R 18 W damage due to a high 30 A current. 225 W (a) 5 A 32 W
(a) 80 W 85 W 45 000 J 1 305 000 J 250 s 140 s 90 W 62 640 000 J 600 s (a) 748 800 J 28 800 J Standby = 138 240 J Full Power = 140 400 J Full for 45 minutes uses up more energy. (a) 306 000 J 2.5 hours 158 400 – 25 200 = 133 200 J 1300 W Power, Current & Voltage (p51 – 52) (a) 1.35 W 18 W 30 A 5 A 50 V 40 V 759 W 3.5 A 12 V 0.52 A 110 V (approximately) Fuses (p53) The fuse protects the flex of an appliance from damage due to a high current. If a occurs, the current can get much higher than is safe (up to 13 A). This can cause dangerous overheating of the flex. The fuse will blow as the current is greater than 3 A. The current is above 3A when the vacuum is turned on although the current drops below 3A when it is in normal operation. More current is required to start the motor. 3 A fuse (I = 0.87 A) 10 A fuse ( I = 5.2 A) 13 A fuse (I = 10.9 A) 5A fuse (I = 4.35 A) Power & Resistance (p54 – 57) P = I V P = I x IR P = I2 R (a) 225 W 32 W
Electricity-and-Energy-Problem-Booklet-sbu8z8.docx