Electrial Systems 13B

Which of the following is not an effect that can be produced by an electric current?

• gravitational effect

• magnetic effect

• heating effect

• chemical effect

Which of the following is not an example of chemical effect?

• electroplating

• electrolysis

• electric bell

• extraction of metals

Which element is usually used to make heating element and why?

• nickel because it has a low resistance

• nichrome because it has a low resistance

• nickel because it has a high resistance

• nichrome because it has a high resistance

The two main types of electrical hazards are

• electric damage and electric shock

• electric shock and electrical fire

• electric damage and electrical fire

• electrical fault and electrical fire

Which of following is not a potential cause for electrical hazards?

• using multiple electrical appliances concurrently

• using electrical appliances in wet conditions

• using electrical appliances with frayed/damaged wires

• connecting too many electrical appliances to one mains socket using an adaptor

Which of the following is not a safety precaution to prevent electrical hazards?

• do not touch electrical switches with wet hands

• do not touch bare or broken wires

• push an item into wall socket

• do not connect multiple electrical appliances to a mains socket using adapter

Which statement best explains how a safety fuse works?

• When the current is too large, the fuse trips and cuts off the current.

• When the current is too large, the fuse increases the resistance to lower the current.

• When the current is too large, the fuse melts and cuts off the current.

• When the current is too large, the fuse redirects some of the current away.

The monthly electrical energy consumption in each household in Singapore is measured in

• Watt (W)

• kilowatt per hour (kW/h)

• kilowatt (kW)

• kilowatt-hour (kWh)

An electrical oven has a power rating of 1800 W. It is used for an average of 1.5 hours each day. Calculate the cost of using the electrical oven for one week if the electrical tariff is $0.30 per kWh.

• $0.36

• $0.81

• $2.52

• $5.67

Answer explanation

Energy consumption each day

= power X time

= (1800/1000) X 1.5

= 2.70 kWh

Energy consumption in a week

= 2.70 X 7

= 18.9 kWh

Cost of usage

• = energy consumption X tariff

• = 18.9 X 0.30

• = $5.67

Which of the following is not a way to reduce energy consumption?

• Use a fan instead of air-conditioner

• Leave the lights on when you leave the room

• Buy and use energy efficient appliances

• Switch off electrical appliances when not in use.